F-/pF!VIETNAM INLAND WATERWAY INTERNATIONAL BANK FORDEPARTMENT / PMU-SW RECONSTRUCTION

AND DEVELOPMENT

INLAND WATERWAYS ANDPORT MODERNIZATION PROJECT

VOLUME IVENVIRONMENTAL ASSESSMENT& ENVIRONMENTAL MANAGEMENT PLAN

FINAL REPORT

JUNE 1996

iNEDECOQ114ether 'ar.ds 'gneigConsultants

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LIST OF REPORTS

VOLUME I EXECUTIVE SUMMARY

VOLUME II INLAND WATERWAYS IMPROVEMENT PROJECT (Main Report)

Annex II - 1 Design ReportAnnex II - 2 Navigation AidsAnnex II - 3 Soil Report

VOLUME III : RESETTLEMENT ACTION PLAN

VOLUME IV ENVIRONMENTAL IMPACT ASSESSMENT &ENVIRONMENTAL MANAGEMENT PLAN

VOLUME V TOPOGRAPHIC MAPS (scale 1:5000)

Book 1: Ho Chi Minh City - Cho Gao (Pl/O to Pl/13)Cho Gao - Sa Dec (Pll/O to P11/211)

Book 2 Sa Dec - Lap Vo (Plil/O to Pill/14)Rach Gia - Ha Tien (PIV/O to PIV/1 9)Rach Soi - Ha Giang (PIV/20 to PIV/32)

Book 3 Cho Lach - Mang Thit (PV/O to PV/20)Can Tho - Ca Mau (PVI/O to PVI/38)

CONTENTS

PART 1: ENVIRONMENTAL ASSESSMENT

1. BASELINE ASSESSMENT 1-1A. General description of the project area 1-1B. Hydrology 1-4C. Geomorphology 1-5D. Water and Sediment Quality 1-10E. Soils and Landuse 1-22F. Aquatic Ecosystems 1-28

2. IMPACTS ON WATER QUALITY AND ECOSYSTEMS 1-40A. Short Term Impacts 1-40B. Medium Term Impacts 1-41C. Long Term Impacts 1-51D. Impact due to changed use of the waterways 1-52

3. ALTERNATIVES AND MITIGATING MEASURES 1-54A. Alternative Project Designs 1-54B. Mitigating Measures 1-55C. Habitat Improvement 1-57D. Environmental Management plan and legal Framework 1-59

PART 2: ENVIRONMENTAL MANAGEMENT PLAN

1. DESCRIPTION OF CANAL STRETCHES AND MEASURES TO BETAKEN 11-1

2. IDENTIFICATION OF ADVERSE ENVIRONMENTAL IMPACTS 11-2A. Short term impacts 11-2B. Medium and long term impacts 11-6

3. DESCRIPTION OF CANAL STRETCHES AND MEASURES TO BETAKEN 11-14A. The Cho Gao canal 11-14B. The Mang Thit 11-14C. The Xa No canal 11-15D. The Rach Soi - Hau Giang canal 11-16E. The Rach Gia - Ha Tien canal 11-16

LIST OF TABLES PART I

Table 1.03 Water quality Xa No canal 1-11Table 1.04 Water quality in Mang Thit River, Vinh Long Province 1-12Table 1.05 Water quality in Cai Rang river & Xa No canal, Can Tho Provincel-1 2Table 1.06 Water quality in Cai Lon river, Kien Giang province 1-1 2Table 1.07 Water quality in Trem river, Minh Hai province 1-1 3Table 1.08 Water quality in Cai San canal 1-13Table 1.09 Survey October 1995 1-14Table 1.10 Data on ph-values collected 1-15Table 1.11 Heavy metals in the waterways 1-15Table 1.12 Pesticides in the waterways 1-15Table 1 .1 3 Description and colour of the soil layers in the 23 cross-sections 1-26Table 1.14 Physical and chemical characteristics of the soil layers in

the cross-sections 1-27Table 1.15 Types of vegetation observed during October '95 survey 1-31Table 1 .16 Aquatic life reported in the waterways of the Mekong Delta 1-34Table 1.17 Macro fauna species and their number at sampling station no 191-37Table 1 .18 Macro fauna species and their number at sampling station no 171-38Table 2.01 Volume & potential acidity of potentially acid soils to be dredgedl-42Table 2.02 Estimated annual acid run-off from pyritic dredge spoils 1-44Table 2.03 Possibility to cover potentially acid sediments with non-potentially acid

sediments 1-46Table 2.04 Yearly acid run-off from dredge spoils 1-47Table 2.05 Period until depletion of the potential acidity of the spoil 1-48Table 2.06 Calculation of the annual acid run-off from land bordering

the canals 1-49Table 2.07 Yearly acid run-off from the spoil and effect of

mitigating measures 1-50Table 2.08 Yearly acid run-off from dredge spoils as a percentage of the

yearly acid run-off from the bordering lands 1-50

LIST OF TABLES PART 11

Table 2.01 Mitigation options 11-7

LIST OF FIGURES PART I

Figure 1.01 Identification of waterway stretches 1-3Figure 1.02 Geology of the Mekong Delta in Viet Nam 1-6Figure 1.03 Physical Zones in the Mekong Delta 1-9Figure 1.04 Salinity Intrusion in the Mekong Delta 1-17Figure 1.05 The Food Chain 1-21Figure 1.06 General Soil Map of the Mekong Delta 1-24Figure 1.07 Land Use in the Mekong Delta 1-29Figure 1.08 Location map of sampling (fishery survey) 1-36Figure 3.01 Habitat Improvement 1-60

Appendix 1

June 1996/4KC1 875.21 /R004/AMS/SPE/lb

PART 1

ENVIRONMENTAL ASSESSMENT

1-1

1. BASELINE ASSESSMENT

A. General description of the project area

1.01 In order to be able to take any decisions or to develop alternativesand distinguish mitigating measures it is necessary, among other things, to gainan insight into ecological resources, the environment, the ecosystems, habitatsand their relationship to man.

1.02 The Mekong Delta has a wide variety of aquatic habitats, includingrivers, tributaries, flood plains, inland swamps, paddy fields, irrigation and drainagecanals, waterways, artificial ponds, estuaries and coastal zones. It is a verysuitable environment for natural biota and all efforts should be made to maintainthis unique environment.

1.03 In the past, most nature and natural values in the Mekong Deltahave unfortunately been destroyed, become extinct or have become desperatelyendangered. The main reason for this destruction is due to the fact that natureeverywhere is only considered as a supplier of consumables (wood, animals etc.).Also the last efforts are made to cultivate the remaining residual natural habitatslike some residual (acid) plains and (mangrove) forests. This is not only a problemin the Mekong Delta, but in the whole of Vietnam. Fortunately the Government ofVietnam has recognised this problem and the loss of bio-diversity, due toextinction of hundreds of species of plants and animals in the country. Accordingto an article in the "Vietnam Investment Review" of 19th - 25th February, theGovernment has undertaken steps to protect Environment and Bio-diversity bycalling on all relevant bodies to prepare and implement laws on environmentalprotection and the International treaty related to biological preservation to whichVietnam is a signatory.

1.04 Because of the dense population of the Delta and the fact thatalmost all the banks of the waterways are mainly occupied by households andcultivated land, there is little left of the original flora and fauna on the banks of thewaterways, creeks and rivers and the adjacent land.

1.05 The faster the population grows in the Delta, the more efficientagriculture will become due to intensification, use of fertilisers and pesticides. Thisin turn means that there will be an increase of different types of pollution. In manyplaces pollution problems already exist. There are still no sewage treatmentfacilities in the area and not every household uses pit latrines, which has led tocontamination with under graded organic matter. Increase of this together with therun off of fertiliser residuals (nutrients) from agriculture will have increasingnegative impacts on the aquatic ecosystems. There is some data which alreadyindicates a severe contamination of water with residuals of pesticides (organochlorine's such as DDT and others).

1.06 The residual of wild flora and fauna is found in the water and to avery small extent on the banks in spite of the fact that almost everywhere thebanks are more or less densely populated and the waters are intensely fished byall imaginable types of fishing gear.

1-2

1.07 Most of the vegetation on the banks is planted by man and consistsof fruit trees and other useful species. In most places, less than a meter behindthe bank region, the agriculture area mainly consists of raised beds on with sugarcane, banana or other agricultural plants are being cultivated. Behind these raisedbeds are large rice fields which are extensively cultivated to yield two or threecrops a year and are monocultures. Virtually no other vegetation is found in therice fields. Removal of the bank vegetation means the removal of most of the landrelated ecological values, which in themselves are not considered to have aparticularly high ecological value but with respect to their surroundings they maybe considered as more valuable.

1.08 Fish, shrimps, crabs and shellfish are an important source of proteinin the Delta. They also have specific functions in the ecosystem of the waterbodies. Due to the fact that no specific information about the aquatic fauna in thewaterways could be found a survey was set up to gather some data. The maingoals were to obtain an impression of local fishing practices and the number ofaquatic species present in the waterways.

1.09 Most of the aquatic species (fish, crustaceans) that still occur in thewaters of the Mekong Delta are "estuarine dependent". They have developedmigration and reproduction patterns that are strongly influenced by the riverregime and the tides. Based on water quality (salinity and acidity), three aquaticenvironmental zones can be identified in the waterways under consideration (seeFigure 1.01):

- Fresh water ecological zone, occurring in stretches 4, 6, 7.- Brackish water ecological zone, occurring in stretches 1, 2, 3, 5, 7, 8.- Acid/brackish water ecological zone, occurring in some places along

stretches 5 and 8.

1.10 The groups of species that make up the estuarine fauna can belisted as follows:

Freshwater species tolerant to limited salinity;- Species living as adults in fresh water, but need brackish water during their

larval development e.g. giant fresh water prawn;- True estuarine species that complete their entire life cycle in the estuary;- Species tolerant to a wide range of salinity;- Marine species which spawn in coastal waters, but live in the estuary

when juvenile;- Marine species which can tolerate some decrease in salinity. They often

visit estuaries because of their abundance in food.

1-3

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1-4

1.1 1 A special factor of importance in the Mekong Delta and thewaterways concerned is the acidity. During certain periods of the year the increasein acidity in the waterways due to acid water run-off from the land prevents moresensitive species from living in the waterways.

1.12 All the circumstances previously described have always beenpresent during the formation of the Delta and as a result the aquatic fauna hasadjusted itself to these changes in physical and chemical conditions. Most of thespecies have adapted to a wide variety of water conditions. Fish, shrimp and crabeasily migrate to more favourable conditions or the conditions they prefer. Thisindicates that changes in water velocity, salinity, acid levels and other morenatural conditions will, in general, not affect the mobiie biota. This is of courseonly true for changes within certain limits.

B. Hydrology

1.1 3 The main waterways to be improved form, together with the MainStreams, Bassac, Mekong and Vam Co Rivers, one open hydraulic system. Thewater levels in this system are mainly influenced by the tidal movement in theSouth China Sea and the Gulf of Thailand, the backwater effects of the MekongRiver discharges and the capacity of the system of creeks and canals to conveythe tidal flow and the river discharge. Moreover, local rainfall and irrigationabstractions have their impact on the water levels.

1.14 In general it can be stated that the canals that need deepening andwidening for navigation purposes, have relatively small cross-sections, andtherefore have small conveyance capacities, when compared with the main riversystem of the Delta. As such, the canals play a minor role in the overallhydrodynamic behaviour of the Delta. Furthermore, the improvement measuresenvisaged will hardly effect this overall picture however, changes within the canalscould be considerable.

1.1 5 Within the framework of the present study, the modelling of theDelta has been carried out in order to assess the present situation regarding waterlevels, discharges and salinity intrusion. The modelling has been carried out withthe help of a dedicated version of the DAC model, by Dr Nguyen Tat Dac of theInstitute of Applied Mechanics, HCMC.

1 .16 In order to study the impact of the proposed canal improvements onthe hydrology, the DAC model was updated and water levels, currents and salinitywere calculated for the present situation. Hereafter follows a summary of theseresults:

Water levels vary from about -1.00 m to + 1.50 m;The largest variations occur on the main rivers. Along the canals thevariation is reduced to about 1.50 m;Velocities are usually limited to less than 1.0 m/s. Only at certain locationsand during extreme circumstances are velocities of 1.50 m/s to be found;Salinity varies considerably along the main waterways. High values arefound between Ba Dinh and Ca Mau, while the salinity is absent betweenCho Lach to about 30 km from Rach Gia and 20 km from Ba Dinh.

1-5

C. Geomorphology

1 .17 The Mekong Delta mainly consists of very young Holocene brackishwater and marine sediments. Only at the border with Cambodia a narrow belt ofold granite and limestone rock outcrops is found together with white clays ofPleistocene age (ref 1).

1.18 A large part of the brackish water and marine sediments consist ofpotentially acid sulphate soils which contain substantial amounts of pyrite (FeS2).The sediments contain pyrite which was formed in brackish water conditions intidal swamps covered with a mangrove vegetation. Pyrite formation takes placeunder the following conditions:

- supply of iron from sediments carried by the river;- supply of sulphates from the sea;- soil reduction caused by the extensive supply of organic material from the

mangrove vegetation;- alternating levels of reduced and oxidised soil conditions caused by tidal

influences.

1 .19 Formation of pyrite is a slow process which takes hundreds of years.When coastal accretion is slow, the conditions are favourable for Pyrite formationover a long period resulting in the deposition of thick layers of pyritic sediments.When coastal accretion is fast, conditions for the formation of Pyrite are shortlived resulting in the deposition of thin layers of pyritic sediments.

1.20 The Mekong Delta was mainly formed in the Holocene period whichwas characterized by a period of gradually rising sea levels. In those days thecatchment area of the Mekong river (Southern China, north-east Thailand, Laos,Cambodia) was largely forested and therefore sediment loads were low. In the first3000 years of the Holocene period, coastal accretion was very low resulting in thedeposition of a thick (4 - 5 m) layer of pyritic sediments having a high percentageof pyrite (up to 4%). These thick deposits are mainly found in the Ha Tien plain.The Ha Tien plain is separated from the remaining part of the Delta by an oldbeach ridge running from Rach Gia to the hills of Tri Ton (ref 2,3). The geologicmap of the Delta is presented in Figure 1.02.

1 .21 During the last 7000 years, increased cultivation of the Mekong rivercatchment area has resulted in an increase in sediment loads. Furthermore, the seawater level has remained more or less constant. Both these factors contributed tocoastal accretion which formed the remaining part of the Delta with shallow layersof pyritic sediments (0.5 - 2.0 m) with a Pyrite content of 1.0 - 1.5%. The pyriticsediments are underlain by sediments formed during marine conditions.

1-6

CAMBODIA

Gl.lf *f >

*. ̂ ,> ~ ; South China sea

~~~~~~~~~~~~~~~~~~'7..

*.a~.C.IIbO'C.1T

LEGEND'

, seGranite rock outcrops++ Pleistocene river deposits ) 12,000 years,O vHolocene brackish water deposits > 5,000 years

Holocene brackisthwaler deposit; < 5,000 years_ Hlolocene river deposits: Itolocene marine deposits

Holocene peat

Figure 1.02: Geology of the Mekong Delta in Viet Nam

1-7

1.22 The recently deposited sediments south-east of the line Soc Trang-Gia Rai do not contain any pyrite. The present rate of sedimentation along thecoast reaches 50-1 00 m/year. In the south-western tip of the Ca Mau peninsular,further away from the river mouth, sedimentation is slower. Here new formationof pyritic sediments are still taking place.

1.23 In the central part of the Mekong Delta, the Mekong river hascreated a classical pattern of floodplains and levees often redistributing the alluvialdeposits by changing course. These alluvial deposits (river and estuarine levees)are usually thin (up to 1.0 m in thickness) and gradually become thinner in thedirection of the floodplains. The alluvial sediments have been deposited on top ofthe pyritic sediments.

1.24 The present shape of the Delta has been influenced by geologicalfaults. The Bassac and the two main branches of the Mekong follow such faults.

1.25 A geo-morphological map of the Delta was prepared whichdistinguishes 26 sub-units within 3 main geo-morphological units (ref 4):

rocky substratum landscape;- old alluvium;- recent alluvium.

1.26 Rocky substratum is found in the north-western part of the Plain ofReeds, the area of the 7 mountains (Bay Nui) and the Long Xuyen Rectangular.Old alluvium is found in the northern part of the Plain of Reeds. The remaining partof the Delta (90%) is recent alluvium including the littoral plain, river depressionsand floodplains.

1.27 In 1974 the Netherlands Delta Development Team (NDDT) dividedthe Mekong Delta into eight main physiographic units and several sub-units (ref 5).These units are certain landscape units, which are relatively homogeneous ingeological formation, topography, soil and land use. The units through which thewaterways are running are:

Unit 1. Coastal Plain

Level tidal flats and relatively small areas of sandy ridges along the coast.The coastal plain is not directly affected by the Mekong flood. Large areashowever, are subject to flooding at high tides from creeks or river branchesif not protected by natural embankments or artificial levees.

Unit 2. Estuarine flood plain

Low levee and adjoining swamps or other low land. Levee sediments varyfrom silts to clays. The (former) swamps deposits are mainly heavy clays.Estuarine deposits overlie potential acid clays at depths ranging from 1 .0m in the swamps to over 2.0 m in the levees. Flood levels in these areasusually exceed 0.2 - 0.3 m for several weeks at a time.

1-8

Unit 3. River flood plain

The extent of the river flood plains is limited, the largest flood plains beingfound in the northern part of the Delta (An Giang Province). Levee depositsare silts and clays, heavy clays are found in the backswamps. Acid soilsoccur locally.

Unit 4. Broad depressions

Broad depressions include a large area in the Plain of Reeds, the LongXuyen Quadrangle and a small part in the Vinh Long province. These areasare part of the estuarine flood plain and are poorly drained. Potential acidsulphate soils are present within 0.5 m of ground level. Parts of thesedepressions remain flooded up to January/February. Those bordering in theLong Xuyen Quadrangle are influenced by salt water intrusion during thedry season.

1.28 The waterway stretches which are to be dredged pass through thefollowing geomorphological units:

1. The Cho Gao canal runs through a high tidal flat into a low tidal flat;2. The Cho Lach canal crosses the levee of the estuarine flood plain at a low

place to connect two river branches;3. The Mang Thit and Ni Co Lai canals connect the Mang Thit river with the

Hau Giang river. The Mang Thit canal starts in the centre of the broaddepression of the Cuu Long river where slightly acid sulphate soils arefound close to ground level. The Mang Thit canal runs south-west whereit connects to the Ni Co Lai canal which cuts through the levee of theestuarine flood plain;

4. The Xa No canal runs from the Can Tho creek to the Cai Tu creek. Itfollows a wedge of the estuarine flood plain running into the broaddepression. The estuarine plain may have been formed by an earlier estuarywhich silted up later;-

5. The Cai Tram canal cuts through a very acid part of the broad depression.The Song Tram Canh Den canal runs south-west through an acid part ofthe broad depression, a small part of the low tidal flat of the coastal plainand finally through an area covered by peat;

6. The Lap Vo canal cuts through the estuarine flood plain;7. The Rach Soi-Hau Giang canal in the direction of the Gulf of Thailand cuts

through the estuarine flood plain, enters the broad depression having acidsoils and near the Gulf of Thailand cuts through the high tidal flat of thecoastal plain;

8. The Rach Gia to Ha Tien canal starts in the high tidal flat of the flood plainnear the town of Rach Gia and continues through the broad depressionwith very acid soils. At the town of Kien Luong, the Kinh Ba Hon cutsthrough the saline swamp of the coastal plain entering the Gulf of Thailand.

1.29 Based on the geomorphological development of the Delta, thicklayers of pyritic sediments which may be excavated during waterway dredging areexpected in stretch 8: the Rach Gia - Ha Tien canal. Pyritic sediments of slightlyshallower depth may be expected along stretches 3 to 7. No pyritic sediments areto be expected in stretches 1 & 2: Cho Gao and Cho Lach canal (see Figure 1.03).

1-9

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i r r~~~~~~[ic | No soil consfraint$w_~~~~~~~~~d DrOn season salinifxt

PS | Permanent salinity

LEJi Shallow flooding

IEI Dcep floooding0 20 40 60 80 lOOKmE ;h ifo

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Figure 1.03: Physical Zones in the Mekong Delta

1-10

D. Water and Sediment Quality

a) General

1.30 Water quality is determined by contents of ions, dissolved, andsuspended materials. The water quality in the canals is mainly determined bysalinity, acidity, organic and inorganic compounds. Information about waterquality is needed to estimate the effects of the dredging on it, in order to predictthe impacts and propose effective mitigating measures. They will be describedbeiow.

1 .31 Very little data is available on the general water quality in thedifferent waterways. No data was found of samples that were regularly taken atthe same spot and analysed over a long period of time, (not even over one year).This considerably hampers the preparation of the impact assessment in relation towater quality, since the canal related ecosystems are strongly influenced by thewater quality in the wet and the dry seasons.

1.32 In addition to the water quality data of the Xa No canal that wascollected in the framework of the MDMP (see Table 1.03) more data was obtainedfrom tables 1.04 to 1.08 showing data of recent (1995) water quality surveyscarried out by the Can Tho University in the waterways under consideration. Thisinformation does not allow for gathering information of water quality parametersduring the different seasons.

1.33 Some additional information was also gained during the field surveysconducted in October 1995 and February 1996 (see Table 1.09 and 1.10).

1.34 The model simulations give important information, especially inrelation to salinity. This is important in order to estimate the discharge of watercontaining unwanted matters and the refreshment of the water bodies.

1.35 To obtain information on heavy metals and pesticides in thewaterways, the sampling and analyses of sediments was conducted at 7 stations.This was conducted because these sediments will be dredged partially and placedon land. The samples were analysed by EPC and the results are presented in Table1.1 1.

1-1 1

Tabile 1.03 Water quality Xa No canal

Date Ph TSS Cond Ca Mg Na K + Alk Cl so4 2 Total Fe Total N Total P Si|__________1 1mg/Il [Psimi Imeq/i1 Imeq/1l Imeqill [meq/li Imeq/ll [meq/ll [meq/l g [mg/Il [mg/li [mg/Il tmg/il

At VI Thanh

I 9/Jun 7.20 118 254 1.05 0.73 0.65 0.046 1.386 0.404 0.756 3.17 0.776 0.167 2.4015/Jul 6.85 93 356 0.87 1.14 0.83 0.096 0.865 0.716 1.185 1.40 1.010 0.229 11.29

At N 14500 canal

20/Jun 6.97 116 290 1.06 0.99 0.80 0.050 1.156 0.433 1.237 2.97 0.713 0.139 2.5315/Jul 6.06 258 307 0.58 1.1.6 0.93 0.096 0.243 0.714 1.938 4.32 1.140 0.146 6.08

At N62 canal

19/Jun 7.06 92 278 1.06 0.87 0.75 0.047 1.241 0.377 0.831 2.19 0.682 0.104 1.9715/Jul 6.66 117 378 0.99 1.51 1.03 0.106 0.630 0.739 1.922 4.41 0.679 0.097 11.25

At N4000 canal

20/Jun 6.95 152 302 1.06 1.05 0.75 0.053 1.093 0.355 1.466 3.58 0.839 0.165 2.29

At Thac Lac bridge

19/Jun 6.99 50 342 1.18 1.12 0.95 0.056 1.205 0.581 1.582 1.89 0.537 0.115 4.0915/Jul 6.58 144 391 0.93 1.42 1.20 0.116 0.67 0.887 1,045 3.18 0.705 0.127 10.85

At Duc bridge

19/Jun 6.98 60 331 1.01 1.02 1.15 0.056 1.276 0.749 1.152 1.76 0.503 0.121 2.03

Source: Environmental Counterpart Team (MDMP), 1992

1-12

Table 1.04: Water quality in Mang Thit River, Vinh Long province

1. Tich Thien StationParameter

Dry season Wet season

Salinity (ppt) 0.00 0.00

pH 7.00 7.00

Seechi disk visibility (cm) 20.00 12.0

N-NH3, (NH,+ NH.') (ppm) 0.10 0.10

P-P0 3- (ppm) 0.30 0.18

SO,2 (ppm)

FeT(Fe2 + Fe"') (ppm) 1.78 3.40

COD (ppm) 7.20 6.00

Heavy metals

Table 1.05 Water quality in Cai Rang river & Xa No canal, Can Tho province

2. Can Tho Station 3. Vi Thawh StatonParsmeter

Dry asason Wetseasn Dry season Wet s on

Salinity (ppt) 0.0 0.0 0.0 0.0

pH 7.5 7.0 7.0 7.0

Secchi disk visibifity (cm) 28 42.0 14.0 12.0

N-NH,,INH,+NH,') Ippm) 0.40 1.70 0.26 0.04

P-PO?, (ppr) 0.26 0.36 0.20 0.22

S0,' (ppm) -

Fe,F;e2 + Fe") (ppm) 2.88 0.92 2.82 2.4

COD (ppm) 10.8 11.2 11.6 11.2

Heavy metals

Source: Xuan, L.N., Faculty of Fisheries, University of Can Tho (1995)

Table 1.06 Water quality in Cai Lon river, Kien Giang province

A. :4ng Su S. :.40- Iightabe 6.|G a*.o fOut tide)

Dry seaon Wet sason :Dry rsea s Wet season Dry sewaon Wet season

Salinity (ppt) 10.56 2.24 7.08 0.45 7.04 0.45

pH 7.5 6.4 7.6 6.8 7.5 6.6

Secchi disk visibility (cm) 10 25 50 30 SO 22

N-NH,,(NH,+NH.') Ippm) trace 0.0 0.0 0.0 0.0 0.0

P PO.P (ppm) 0.15 0.30 0.10 0.35 0.10 0.30

Fe, (Fe" + Fe") (ppm) 0.2 0.3 0.15 0.30 0.15 0.30

COD /ppm) 14.0 21.4 8.8 10.4 11.2 8.8

Source: Hang. T.K., Aquaculture Research Institute N°2 (1991)

I-1 3

Table 1.07: Water quality in Trem river, Minh Hai province

7. Tac Thu, Thoi BinhParameter Dry season Wet season

Salinity Ippti 16.5 2.0

pH 7.0 7.3

Secchi disk visibility (cm) 32.0 14.5

N-NH3T(NH3+NH4,) (ppm) 0.44 0.20

P-PC,3- (ppm) 0.38 0.14

SO42 (ppm)

FeT(Fe2 , + Fe3" (ppm) 1.25 2.5

COD (ppm) 7.2 7.2

Heavy metals

Source: Thuong, N.V., Faculty of Fisheries, University of Can Tho (1990)

Table 1.08: Water quality in Cai San canal

S. Thot Not Station 9. Linh Quynh Bridge 10. Dong Ho Station(1) (2) (2)

Parameter Dry season Wet season Dry season Wet sea- Dry season Wet season

son

Salinity (ppt) 0.0 0.0 0.96 0.13 21.12 20.16

pH 7.5 6.5 7.2 5.3 7.8 7.8

Secchi disk visibility (cm) 41.5 70 30.0 80.0 50.0 90.0

N-NH2T (NH3+ NH4 ) (ppm) 0.08 0.05 0.0 0.0 0.0 0.0

P-PO,3 (ppm) 0.18 0.16 0.10 0.20 0.15 0.15

S042 (ppm) - - -

FeT (Fe2 -+ Fe3T) (ppm) 1.46 0.44 0.20 0.25 0.20 0.20

COD (ppm) 8.2 8.8 14.4 4.8 12.0 16.8

Heavy metals * .

Source: (1) Xuan, L.N., Faculty of Fisheries, University of Can Tho (1995)(2) Source: Hang, T.K., Aquaculture Research Institute N°2 (1991)

1-14

Table 1.09 Survey October 1 995. Physical parameters, Settlements, Fisheries, Waste

Station Physical parameters Settlements Flshihg Waste_ e : : ~~~~~~~~~~~~~~~~gear

EC In p S/m T°C Colour visibilfty Current m/s Width in mh Organic Anorganic

Stretch 11 4230 28.8 grey/brown 0.05 1.5 80 5% N&S t 0

Stretch 32 150 30.0 brown/grey 0.2 0.6N 100 30%N,20%S t 0 03 161 30.5 brown/grey 0.2 0.6N 90 20% N&S 0 0

Stretch 4+54 140 30.0 grey/brown 0.2 2S 700 100% N&S 00 005 140 30.0 brown/grey 0.1 OS 80 40% N&S gn,ft,b 0 06 143 30.2 brown/grey 0.1 O.S 80% 100% N&S 00 007 156 29.2 brown/grey 0.05 0 100 O%N,20%S gn,ft,b,s

8 Caillon r. 207 30.6 brown/grey 0.05 0 300 20%N,20%S b,s.t9 770 28.9 grey/brown 0.05 0 50 20% N&S10 850 31.6 greenish 1 0 80 10% N&S

Stretch 7+811 114 30.6 brown/grey 0.1 n.e. 60 100% N%S 0 012 117 31.2 brown/grey 0.1 n.e. 50 2%N,50%S 013 119 31.8 brown/grey 0.1 n.e. 50 30%N,75%S 014 121 29.8 brown/grey 0.1 n.e. 50 50%N,95%S 015 122 30.8 brown/grey 0.1 0.8 S 50 50%N,95%S gn,b 016 125 30.8 grey/brown 0.1 1 S 50 50%N,95%S s 0 017 168 31.4 grey/brown 0.1 1.3 S n.e. 100% N&S 018 185 30.9 grey/brown 0.5 0.3 S 100 60%N,100% 0 019 2200 30.9 green/grey 0.8 0.1 S 80 S b 020 2340 30.9 greenlble 0.4 0.1 S 50 5% N&S b 021 6910 30.7 green/grey 0.9 0.3 S 60 10%N,30%S 0 022 4330 31.1 green/brown 0.7 0.4 N 70 2%N,20%S 0 023 4460 31.2 green/brown 0.6 0.8 N 60 2%M,60%S 024 5360 32.0 brownish 0.5 0.7 30 1%N,10%S 00 00

95%N,100%S

t - Trawl net 0 - incidental patches along the embankmentgn - gill net 00 - scattered across the entire embankmentb - bush N - northern banks - scoop net S - southern bank

I-1 5

Table 1.10 Data on Ph-values collected

Canalistretch | Location P H

Xa No, Vi Than 5 7

Trem Can Denh 10 7

Ong Doc river 1 1 7.1

Rach Spo Hau Giang 16 7

Rach Gia ha Tien 20 3.8

Rach Gia ha Tien inland pond 1 9 4.1

Rach Gia Ha Tien new canal 19 4.8

Table 1.11 Heavy metals in the waterways

Parameter Resuits [mg/kg]

1 la 4 9 12 14 20

% of Dried sample 51.61 28.09 43.05 24.52 52.26 47.40 22.48

Cr 67 85 61 79 65 69 45

Ni 120 150 92 110 120 120 81

Cu 39 67 39 33 31 32 33

38 160 200 38 29 30 49

Hg 0.16 0.22 0.27 0.27 0.10 0.03

Table 1.12: Pesticides in the waterways

Parameter :Resuhts rpglkg]

1 4 9 :12 :14 20

Lindane 1.77 3.07 15.93 4.13 2.32 0.44

Aldrin 1.40 2.42 - 1.31 1.69 3.61

Dieldrin 3.34 4.67 5.75 0.96 2.09 5.02

Endrin 4.59 7.99 3.76 1.05 1.99 4.57

DDE 2.57 3.46 2.72 1.08 1.60 3.76

DDT 5.49 1.91 1.18 1.42 5.64 8.50

Alfa beta endosulfan 1.76 3.66 0.34 0.90 2.46 1.92

1-16

b) Salinity

1.36 Extensive studies have been carried out in Viet Nam on the salinityintrusion in the Mekong Delta, amongst them the Mekong Delta Salinity IntrusionStudy Project (1983-1991) and the Thematic Studies on Water ResourcesManagement and on Salinity Intrusion carried out in the framework of the MekongDelta Master Plan (1 991-1 993). Modelling studies have been carried out to assessthe impact of water use scenarios on the salinity intrusion (see Figure 1.04).Historical data as well as the model results indicate that in the Cho Gao canal, theRach Gia - Ha Tien canal and the Song Trem Canh Den canal will containpermanent or during certain periods of the year in the dry season brackish to saltwater. The salinity is of major importance for the presence of aquatic biota.

1.37 In order to get a better impression of the salinity intrusion in thewaterways for the existing situation and future water management scenarios,additional modelling has been carried out. With this new model the impacts ofcanal widening/deepening on hydraulic and salinity conditions were determined.

1.38 Salt intrusion especially during the dry season causes problems foragriculture and reduces the possibilities to use water for other (household)purposes. There may be some increase in salt intrusion due to the growingdemand for fresh water by the extending agriculture efforts. The construction offlap valves to prevent salinity intrusion as foreseen for the region south east of theChac Bang canal will significantly affect the intrusion of salt water in the Xa No,the Chac Bang canals and the water bodies connected hereto.

c) Acidity

1.39 Acidity washed into the canals may cause massive kills of aquaticlife in canals or river/estuarine/coastal areas receiving acid drainage water (ref10,11 ,12). Effects of water acidity on (European) fish is illustrated in Table 1 .12.

1.40 Research on the toxicity of acid water has been carried out inAustralia. Acidity is caused by high amounts of aluminium, iron and H+. Theseions are very toxic to most aquatic life. In parts of north eastern Australia theonset of heavy rains causes a 'first-flush" run-off and drainage of phytotoxicwater with properties including low pH and high concentrations of dissolvedaluminium. These waters have caused massive fish kills (ref 10, 11, 12). Inaddition, an ulcerative fish disease, epizootic ulcerative syndrome (EUS), hasshown a pattern of seasonal recurrence in eastern Australia which also relates tothe onset of rains.

1.41 The disease is also spread over South east Asia. It is thought thatchemical properties related to acid water causes skin damage in which anoomycete fungus, Aphanomyces sp., can invade and cause the ulcers (Callinan etal 1992). Other studies also mention fish kills and EUS as the result of run-off oftoxic acid water. No information was found about the resistance of the fishspecies and other biota present in the Mekong Delta against acidity. This impliesthat no strict limits can be defined about the tolerance of the species concerned.Eggs and larvae are supposed to be somewhat less resistant to toxic acid waterhowever, there is no firm evidence supporting this. Only the measured value of pH3.8 in the Rach Gia - Ha Tien canal and the presence of fish in that canal at thesame time suggest a certain resistance of at least some fish species.

1-17

. _T~4.CAM BODIA _ '

THAILAND <<

SOUTH CHINA SEA

~~~~~~~-LEGENDSo N . No Sainity intrusion or S4 4

= Duration below 3 monfhs.Si IT = Durotion from 3 to 6 rnonths.52 V,!M Dura:iofn rrom 6 to 9 mnontms.

a 2C -0 ;3 go 10I I Duroteon over 9 msonthS.EM All of ycar

r.ti Dora from 1977 ro 1 390

Figure 4.0, Sa i * Ity Irusio%n in the MoAonr.n Denta

i-18

d) Nutrients

1.42 Data suggests that there are no high amounts of nutrients in anyperiod of the year. This means that the waters are not unacceptable polluted by'P' (max. of 0.4 mg/l) or 'N' (max. of 0.5 mg/I). In all the waterways there isalways a certain water movement, throughout the year due to tides and becausethey have open connections to the main rivers and the sea. Although the relativelyhigh amounts of fertilisers (80 - 120 kg/ha/year) and Luman waste flow directlyand/or indirectly through the different waterways, most nutrients are efficientlytransported to the sea. According to the investigations by the Mekong Committee,Water Quality Monitoring Project the maximum average total dry season nitrogenconcentration in the main streams (Mekong and Bassac) is 0.32 mg/I rising to 0.37mg/I during the wet season near Tan Chi and My Tho.

1.43 The total phosphate concentration in the waterways was about 0.14mg/l during the dry season rising to 0.2 mg/l in the wet season. The nitrate andphosphate concentrations measured by the EPC at several stations do not showhigher values which indicates that the Mekong waters are slightly contaminatedby nutrients (unpolluted rivers should not show phosphate concentrations of morethan 0.01 mg/I). However, the nutrient content is still very low when comparedto contaminated rivers like the river Rhine where at the Dutch-German bordervalues up to 21 mg/l total N, and up to 3.6 mg/l total P are measured.

1.44 In the canals, especially in ponds in the paddy areas and populatedareas, nutrient levels in surface water are much higher. N-concentrations of 0.1 -0.3 mg/I, and in some places over 1.0 mg/l were found. Phosphate

concentrations of 0.8 mg/l maximum and maxima of slightly over 1.0 mg/lnitrogen concentration were found. The WHO's guideline for nitrate concentrationin drinking water is 10 mg/I. The World Heath Organisation (WHO) does notconsider phosphates in drinking water. In guidelines concerning several countries,concentrations of 0.7 (EEC-standard) to 5.0 mg P205/I (Trinh) are mentioned. Thelimit for Carp culture ponds is 0.26 mg P/I (US-standard).

1.45 In terms of human health risks, the present concentrations ofnutrients in the rivers, canals and even the fields are still below dangerous levels.Water containing a total P over 0.15 mg/l and a total N over 0.1 mg/I must beconsidered as eutrophic. This explains the presence of the different biota in thewater bodies. Waters with higher concentrations of nutrients are more productive(biomass of plants, algae and aquatic fauna) and are therefore endangered bycontamination of water hyacinths.

1-1 9

e) Pesticides and heavy metals

1.46 The expansion of agricultural efforts in the Mekong Delta, and theintroduction of HY-rice varieties show an increasing need for pest control. Everyyear, thousands of tonnes of chemical pesticides are used in the Delta. It can beexpected that the use of pesticides will continue to increase every year.

1.47 The Organo chlorines like DDT and heavy metals like mercury whichcontain pesticides are particularly dangerous. They are persistent and accumulatein the fatty tissues of animals and man. High levels of these pesticides in tissuesis toxic. Also organisms that consume other organisms accumulate higher levelsof these chemicals in their tissues. For instance, birds of prey and fish eating birdsare affected by high levels of these pesticides and are not able to reproduce. Mantoo, being at the end of the food chain will accumulate pesticides in his body (seeFigure 1.05). This affects his heath and unacceptable amounts of pesticides mayalso be found in mother's milk. It is generally accepted that these pesticides arevery dangerous and therefore most countries throughout the world have bannedthe use of organo chlorine's.

1.48 Although many pesticides are banned and the use of others isrestricted by decision of the Ministry of Agriculture and Food Industry of VietNam, (Decision N23/BVTV-KHKT/QD 1992)(ref. 26), organo chlorines such aslindane, and endosulphan (possibly DDT also) are still used.

1.49 Concentrations of pesticides have been studied in the surface of theHau Giang province by EPC in collaboration with the provincial department ofsciences in 1989-1 992 (Ref. 25 Vol 5). They found for instance in the Xa Nocanal near Vi Thanh 3.30 pg/I. For drinking water the maximum concentration inmost countries may not exceed 0.1pg/l. Because sampling was carried out severalweeks after crop spraying the maximum concentrations in the canals could evenbe much higher. Other stable pesticides are often more toxic to other organismsthan the target ones e.g. Pyrirthroids are highly toxic to cold blooded organismssuch as fish and crustaceans. All those pesticides will affect organisms such asfish, shrimp and other crustaceans. The levels of concentrations of pesticidesfound in different types of surface water during the EPC study is alarming.

There are no data about the use of pesticides containing heavy metals like mercuryand it is unlikely that in the past or just recently, substantial amounts of heavymetals were spread over the Mekong Delta. Heavy metals are dangerous becausethey can accumulate in the food chain in the same way as persistent organochlorines. All the heavy metals present in and along the waterways are most likelyto be there naturally. In sediments etc. higher amounts of heavy metals can befound. They originate from erosion of the soils and mountains in upstream regions.

Results of the analyses (pesticides and heavy metals) show that theconcentrations of most of the heavy metals as well as pesticides are lower thanthose considered internationally acceptable for whatever use. Tables 1.11 and1.12 present the results of the bottom sample analyses.

1-20

There is one exception and that is the concentration of nickel which appears to berelatively high. When the nickel concentrations are compared to thoseenvironmentally acceptable in Holland, one discovers that the soil falls into thecategory "Class 3" material which is classed as polluted.

The bottom samples were all analysed in Viet Nam by EPC and the results arepresented in Tables 1.1 1 and 1.12. The high concentrations of nickel weresomewhat surprising and therefore it was decided to analyse a few samples in theNetherlands. The results of the analyses in the Netherlands (see Appendix 1 at theend of this report) showed that the material was a "Class 0" or a "Class 1"material which is unpolluted and therefore can be placed on arable land. Theclassification of dredged spoil in the Netherlands is given in Appendix 1 also. Inaddition, the concentrations of nickel were far lower than that measured in VietNam which accounts for the lower classification.

It can be concluded that is will be necessary to execute a more detailed samplingprogramme and laboratory analyses on heavy metals and pesticides. The resultsshown in Tables 5.10 and 5.11 are only from bottom samples and therefore it isrecommended that in the future bottom samples are also taken over the vertical.

- i

c')

co

OWALL. MOM

+++ ~~~~FOOD CHAIN

ZOO PLAI. N 0 DEAD OWOANIC

PLANTU ALOAE 4. BACTERIA

+AMOUNT OF ACCUMULATED PEGrICtDES.

1-22

E. Soils and Landuse

1.50 In the course of the last 400 years, increasing areas of the MekongDelta have been reclaimed for agriculture by removing the natural vegetation,mainly consisting of Melaleuca forests. The slash and burn technique used, alsoresulted in the burning of peat in the broad depressions. From the second half ofthe 1 9th century to the present day, a dense network of canals was excavated fortransportation, irrigation and drainage purposes. The disappearance of peat as anatural water buffer together with the increased drainage through the canalnetwork resulted in a lowering of the dry season ground water levels throughoutthe Delta.

1.51 In the broad depressions where pyritic sediments were only coveredby a thin layer of alluvial sediment, lowering of the dry season ground water levelsresulted in exposure to atmospheric oxygen followed by oxidation of pyrite and therelease of large amounts of acidity. In the levees of the river and estuarine floodplain, air-exposure of pyritic sediments was limited since the pyritic sedimentswere covered by a thick layer of alluvial sediments.

1.52 Depending on the redox-conditions in the soil and the time ofoxidization, the end-product of the oxidation of Pyrite can be:

- ferrous iron, sulphate and hydrogen ions;- .. the straw-yellow mineral Jarosite (K(Fe)3(SO4)2(OH)6), sulphate and

hydrogen ions;- ferric-(hydro)-oxides, sulphate and hydrogen ions.

1.53 The pyritic sediments in the Mekong Delta are all heavy clays whichmainly comprise silicon and aluminum-oxides. At low pH values, the clay-mineralsare unstable which results in the release of soluble aluminum.

AI(OH)3 CIy.minmls + 3 H+ --> Al3+ + 3H20

1.54 In the USDA classification, the pyritic sediment is described as thesulphitic horizon (characterized by the permanently reduced conditions and thepresence of Pyrite). The oxidised pyritic sediment is indicated as a sulphurichorizon (Jarosite being present and pH below 3.8). Acid sulphate soils arecharacterized by the depth of occurrence of the sulphitic and sulphuric horizons.A first distinction can be made between potential acid sulphate soils (PASS) andactual acid sulphate soils (AASS). The classification of acid sulphate soils in theMekong Delta based on the USDA classification can be summarized as follows:

Code Soil tvpe Deoth to Deoth toSulPhitic Sulohurichorizon horizon

Sp1 severe potential acid sulphate soil 0 - 50 cmSP2 potential acid sulphate soil 50 - 100 cmSj1 severe actual acid sulphate soil - 0-50 cmsj2 actual acid sulphate soil 50-1 00 cm

1-23

1.55 Several soil maps have been prepared of the Mekong Delta, includingthe soil map of the Mekong Delta (scale 1: 250.000) by the National Institute ofAgricultural planning (NIAP) in HCM-City (ref 6) and the Soil Map of the Trans-Bassac area, prepared by the University of Can Tho (ref 7), see Figure 1.06. Bothmaps are mostly based on the USDA soil classification.

1.56 The soil map prepared by NIAP identifies eight main soil units whichare described below:

Soil unit: % of total delta area

Sandy soils 1.1Saline soils 19.1Acid sulphate soils 41.0Alluvial soils 30.4Peaty and Muck soils 0.6Grey soils 3.5Red-Yellow soils 0.05Eroded soils 0.2

1.57 Based on the soil map of the Mekong Delta by NIAP, AASS andPASS are encountered in the following stretches over the following distance (inkm):

No Stretch. SP, SP2 Si, 1i21. Cho Gao canal - - - -

2. Cho Lach canal - - - -

3. Mang Thit + Ni co lai canal 0.75 - 1.0 9.04. Xa No canal 2.75 - - -

5. Cai tram canal 0.75 - - -Song Tram Canh Den canal - - 5.75 23.5

6. Lap Vo canal - 2.5 - -

7. Rach Soi-Hau Giang canal - - - 19.758. Rach Gia to Ha Tien canal - - 28.5 25.00

Ba Hon canal 5.0 0.75total: 4.25 2.50 40.25 78.00

1-24

. I~~~~~~~~~~2.N

I CAM,O!JIA Kt 1. - Z MO CHI I.Almm CiTY

;u1lf of Thailand

Suth China sea

= 6111 | Severely a-id W#0te soils (as.s)M.eraWtely and sliguy acid suiphala soils (ass)

F Severely a.s.; with dry season salinity I

[ , *--i Moeradlely and sliohtly a.ss with dry sason

I ~"4'* Potential ass with permanent salinity.

Permaiwently saline $soI

JJJ Dry season sairne soils

~ Grey soils

mountaineous soils

Figure 1.06 General Soil Map of the Mekong Delta

1-25

1.58 As can be seen in 1.57, acid sulphate soils pass through the entirestretch 8: the Rach Gia to Ha Tien canal together with the Ba Hon canal. Soilsalong this canal equally consist of Sj1 and Sj2 soil types. Less acid sulphates soilsare crossed in stretch 7: the Rach Soi-Hau Giang canal with mainly Sj2 soil types.The same length of acid sulphate soils are encountered in stretch 5, mainlyconsisting of Sj2 soil types.

1.59 During phase 11 of the project a soil survey was executed toinvestigate the presence of potentially acid sediments in the subsoil. In 23 pre-determined cross-sections the soil profile was investigated using a soil auger. Theinvestigation started at the top of the canal bank and penetrated a depth of 4 to5 meter. Soil colour and texture of the lithology was described. Potential acidsediments were identified using the quick oxidation test. Samples were collectedfrom the potential acid sediments and taken to the laboratory for analysis ofchemical and physical characteristics. The laboratory analysis comprised tests onwet bulk density (WBD) and total potential acidity (TPA).

1.60 The results of the soil survey are presented in a report "Draft reporton soil and landuse for the main inland waterways Ho Chi Minh City - Kien Luongand Ho Chi Minh City - Can Tho - Ca Mau", prepared by the University of CanTho. The results of the survey are summarized in Tables 1.13 and 1.14. Moredetails can be found in Chapter 2 of Annex 11-3: "Quantification of the release ofacidity from dredge spoils compared to acidification from surrounding land".

1.61 The results of the soil survey indicate that very little potentially acidsoil layers have been found in the Cho Gao, Mang Thit, Rach Soi - Hau Giangcanals and eastern and central sections of the Xa No canal.

1.62 In the western section of the Xa No canal, the Tat Cay Tram canal,Tram Canh Den canal and Lap Vo - Sa Dec canal, potentially acid sediments arepresent which comprise moderate to severely potentially acid grey to dark grey(sometimes black) heavy clay. Non-potentially acid sediments are found below thepotentially acid sediments. -The underlying non-potentially acid sediment usuallyconsists of grey to very grey sandy or silty clay. The lighter texture can beexplained by the fact that this sediment has been deposited under more turbulentmarine or estuarine conditions.

1.63 In the Rach Gia - Ha Tien canal, the potentially acid sediments weredeposited in an earlier stage of Delta development. The thickness of the sedimentsis usually more than the above mentioned sediments: 3-6 m. Below the potentiallyacid sediments, an old alluvial sediment is found of the pleistocene epoch. Theseold alluvial sediments consist of moderately to severely potentially acid grey tovery grey (sometimes black) heavy clays. The underlying old alluvium consists oflight grey to grey heavy clay, usually with a very low organic content and greatershear strength when compared to the darker, softer and more organic potentiallyacid sediment.

Table 1.13 : Description and colour of the soil layers in the 23 cross-sections

PYRITIC LAYER 1: PYRITIC LAYER 2;: NON PYRITIC LAYER:

Canal: pro.description pyritic colour description pyritic colour description matrix

sediment code sediment code sediment colour

Cho Gao C1 n.r. n.r. not present

Mang Thit C2 n.r. n.r. not present

Xa No C3 n.r. n.r not presentC4 dark grey heavy clay 2.5Y4/0 not present dark grey fine sandy clay 1 OYR4/1C5 very dark greyish brown heavy clay 1 OYR3/2 not present grey clay 5Y5/1

Tat Cay tram C6 dark grey heavy clay 2.5Y410 not present dark grey clay 5YR4/1

Tram Canh Den C7 dark reddish brown heavy clay 5YR312 grey heavy clay 1 OYR5/1 dark grey fine sandy clay 5Y4/1C8 dark grey heavy clay 7.5YR410 not relevant dark grey fine sandy clay 7.5R4/0C9 dark greyish brown heavy clay 2.5Y4/2

Lap Vo-Sa Dec C12 dark-very dark grey silty clay 2.5Y4/0-3/0 not present dark grey fine sandy 2.5Y4/0loam

Rach Soi-Hau C13 dark grey silty clay 2.5Y4/0 not present grey silty clay 5Y511Giang C14 not present

C15 not presentC16 not presentC17 not present

Rach Gia-Ha C _ not presentTien C19 black clay 2.5Y2/0 dark grey silty clay 5Y41t

C20 dark-very dark grey silty clay 5Y4/1-3/1 not presentC21 reddish brown silty clay 5YR4/3 dark grey clay loam 5Y4/1 light grey-grey 1 OYR6/1C22 grey-dark grey silty clay 5Y511-411 light grey-grey 5Y51611 light brownish clay 2.5Y612C23 dark grey heavy clay 5Y4/1 not present

Table 1.14: Physical and chemical characteristics of the soil layers in the cross-sections.

PYRITIC LAYER 1 PYRITIC LAYER 2 NON PYRITIC LAYER

Canal Pro. depth to D WDB TAwet Alwet from to D WDB TAwet Alwet from to Dfrom

cm cm cm m g/cm3 mm01+ mmoll+)/ cm cm m g/cm3 mmol(+)/ mmol(l+ )/ cm cm m

L 100 gr 100gr 100 gr 100 gr

Cho Gao C1 335 357 0.2 1.63 23 4 n.r. n.r, n.r. n.r n.r. n.r.

Niang Thit C2 n.r. n.r. n.r. n.r. n.r. n.r.

Xa No C3 0 0 0.0 0 0 0 0 0 0.00 0 0C4 160 360 2.0 1.42 30 58 0 0 0.0 0 0 0 360 460 1C5 100 180 0.8 1.29 09 12 0 0 0.0 0 0 0 180 400 2.2

Tat Cay tram C6 95 230 1.4 1.53 93 6 0 0 0.0 0 0 0 230 280 1.5

Tram Canh C7 40 150 1.1 1.08 144 18 150 320 1.7 1.48 81 7 320 420 1Den C8 120 220 1.0 1.51 50 5 5 0 0.0 0 0 0 220 350 1.3

C9 50 120 0.7 1.51 43 8 120 290 1.7 1.5 16 4

Lap Vo-Sa C12 268 430 1.6 1.43 36 5 0 0 0.0 0 0 0 430 500 0.7Dec

Flach Soi-Hau C13 240 260 0.2 1.62 15 2 0 0 0.0 0 0 0 260 400 1.4G;iang C140 0 0.0 0 0 0 0 0 0.0 0 0 0

C15 0 0 0.0 0 0 0 0 0 0.0 0 0 0C16 0 0 0 0 0 0 0 0 0.0 0 0 0C17 0 0 0 0 0 0 0 0 0.0 0 0 0

Flach Gia-Ha C18 0 0 0.0 0 0 0 270 400 1.3 1.51 1 1lien C19 112 165 0.5 1.39 38 8 165 400 2.4 1.37 104 12

C20 190 400 2.1 1.55 93 16 0 0 0.0 0 0 0C21 110 153 0.4 0.43 57 14 153 350 2.0 1.23 116 18 350 400 0.5C22 150 250 1.0 1.56 51 6 250 400 1.5 1.55 43 5C23 250 320 0.7 0.59 34 5 0 0 0 0.0 0 0 0 320 400 0.8L

1-28

1.64 The water quality of canals, creeks and rivers crossing acid sulphatesoils is strongly affected by the presence of these soils. Acidification of the watersis characterised by a decrease of pH together with an increase of theconcentration of soluble aluminum, ferrous- and ferric-iron and sulphate. Therelationship between pH and soluble aluminum and iron is controlled throughchemical equilibria, mainly the precipitation of the hypothetical mineral AISO4OHand gibbsite A12(S04)2.

1.65 The landuse along the waterway stretches has been investigatedduring the soil survey which was executed during the second phase of the project.A total of 23 cross-sections were examined. The results of the survey aresummarized in Figure 1.07.

F. Aquatic Ecosystems

a) Water Quality and Vegetation

1.66 In order to obtain an up to date impression of the environment inand along the waterways, a field trip was made in October 1995, while anadditional survey took place in January 1996. Attention was paid to the followingitems in and along the waterways:

- presence of visible submergent vegetation;- presence of visible emergent vegetation;- presence of floating vegetation;- the vegetation along and on the banks of the waterways;- the used fishing methods;- presence of fish, birds and other biota;- presence of settlements;- pollution by floating organic and inorganic waste.

1 .67 The results of the field surveys are presented in the phase 1 reportand reflect the situation at that moment. The results of the two surveys in respectto the system can be summarized as follows (see also the observed types ofvegetation presented in Table 1 .1 5:

Visibility and the colour

Water visibility is low. The grey/brownish water does not exceed a visibilityof more than 20 cm which implies that there will not be any large visualhunting species present in these water bodies. Only in those stretchesknown to be more acidified, is the visibility better, due to the flocculationof sediments by Fe2SO4. Here, the maximum visibility of 100 cm wasfound in stretch 5 and in stretch 8.

T1I

(0C:

LAND USE INVENTORY G

CD

C-~~~~~~~~~~~~~~~~~~~~~~~~~~ -,DbC:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Z

(~~~~~~~~~~~~~p ~~~ ~ (

N~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~O . . .... ...

r r~~HAILAND OULP F

(1)] Jv _ X l(II/ ~ ~ o X vnF7-wLEE0\,

CI ~ ~ ~ ~ /DNSmolEKal| eictt oot \8 }~~~~~~~/coz Eryt :1et _4A

cc'~/fX 1err^rc-z10- 0t\

C~~~~~~~~~~._1.j.................j;j......,.. W.iI

(D

1-30

The temperature

The temperature in October 1995 varied between 28.8 and 32 "C. Nonoticeable fluctuation on differences in temperature in the waterways wasestablished.

Settlements

The density of settlements give some indication of the amounts of organicand inorganic waste and pollutants. It also gives insight into the pressureon natural biota. In general, the banks of the waterways show a relativelylarge number of settlements everywhere. Only the northern bank of theRach Gia Ha Tien canal showed less density of settlements.

Submergent Vegetation

Submergent vegetation was only seen in stretches 4 and 5. The plants lookvery similar to Ceratophyllum sp. In January 1996 this species was seennear location 20 in the Rach Gia - Ha Tien canal but only floating and notattached to the bottom. This means it could have come from somewhereelse. Also, some Nymphaidae with floating leaves were observed in thesouthern part of stretch 4.

Emergent Vegetation

Emergent vegetation was found along all the waterways. These include theNipa palm (Nipa fructicans), Cane (Sagarum officinalis) some graminea andcyperacea. The Nipa palm was found in almost all waterways. It may beexpected that it has been planted by man in the fresher parts of the waterbodies. There are many mangrove trees (Avicennia alba), especially in themore brackish areas. A more dense natural emergent vegetation is seenalong the banks of the Cho Gao canal. This is due to the presence ofshallow mud flats on with the mangrove vegetation can settle. Here too,the wide of such a vegetation is not more than about 5 m.

Floating Vegetation

The Water Hyacinth and, in some places, a few Azollidae were observed.The Water Hyacinth is more abundant in the southern part of stretch 4. Itis envisaged that this species will increase due to the growing use offertilisers as a result of increasing population and agriculture.

Vegetation on the Banks

The vegetation on the banks is dominated by planted trees (such asCoconut), different species of shade and wood providing trees. A treewhich clearly stands out is the Kapok. Besides the coconut and the kapok,fruit trees are found everywhere in large numbers. Among these: papaya,banana, citrus, mango are the most dominant ones. Due to their elevationthe banks are suitable for cultivating sugar cane. This ideal growingconditions were observed along the Mang Thit canal and the Lap Vo - SaDec canal.

1-31

Table 1.15: Types of vegetation observed during October '95 survey

.o .o ~E EE EEE

O G 0 0 00 O

c 3 *3 oo oo33.

E, S. S o o o .3 .3

00 00 00 00 00 00 00 00 00 00 00 00 00S °

E ..

8 Q 99 339 oo e0 00 no oo *- *- 8i fi 3S ° 3.S

83 . 3 3 * 00 00 0e 00 e 0 ** * e. 3e 3. 3. >ee

e 1 I 8i 8 -e

1-32

Table 1 .15: Types of vegetation observed during October '95 survey

(cont)

0 00 00 00~~~~~~~~~

t o~~~~~S

i g o oo o0 0 0 0

_ .0 o

-A * -0 0 0 0

-80 ~*80o gg g § o S

o So * ~o*o 00 so so

'. 00 0 00 00 00 00 00~~~~~~~.i e

1-33

b) Fish, shrimp and crab

1.68 There was very little information on fish and fisheries in the canalsand therefore a programme based on interviews with local fishermen was set up.This was extended in November 1995. Every 20 - 30 km interviews were heldwith local fishermen.

1.69 The following Questions were asked and points established.

1. What species (Latin or Vietnamese names) of fish, shrimp, crab and edibleshellfish can be found in the waterways ?

2. Which local fishing methods are used ?3. Estimate the number of fishermen & types of fishing practices adopted per

kilometer ?4. Trends from the past:

a) Has the production increased/decreased over the last ten years ?;b) Have certain fish species become smaller/larger over the last 10 years?

6. If yes, what are the causes ?7. Which fishing methods are not allowed in the waterways ?

1.70 The fishery survey was carried out by the department of fisheries(at present part of the department for agriculture) of the University of Can Tho.Table 1 .1 6 presents the various species of fish, shrimps and crabs reported in thewaterways. The locations are indicated in Figure 1.08.

1.71 It should be noted that the survey was only based on interviewsheld among local fishermen. The amount of information gained from the survey isnot considered to be enough to draw any reliable conclusions however, it can beseen as an indication. The result of the proposed monitoring programme will givemore reliable and detailed information. The results show a larger number ofspecies in the Cho Gao canal. This could be due to the fact that in this canal freshwater and brackish water species are found during different times of the year andthat this canal is usually used by migrating species. A lower number of specieswere mentioned by the fishermen in the Rach Gia - Ha Tien canal. This may becaused by low pH values due to the influx of acid water.

1.72 The various types of fishing equipment and fishing practices adoptedare as diverse as they are widespread. There are professional fishermen using thetrawl, beam trawl, scoop nets and the larger nets such as seize nets, encirclingnets, fence nets and trap nets. It is difficult to divide the fishermen intoprofessional and non professional as almost everybody in the Delta fishes to somedegree. The fish survey and the field trips clearly indicate that the inlandwaterways are heavily over fished. It is even amazing that fish are still found incertain areas.

1.73 This leads to the conclusion that the standing stock must be (very)low. If better managed, by measures to reduce the efforts, by banning fishing gearwhich catches most of the smaller not yet matured fish and strict rules on themesh sizes, the production and seize of fish from the waterways will increasesubstantially. If in addition, better habitats are realised the fish production willincrease even more.

1-34

Table 1.16: Aquatic life reported in the waterways of the Mekong Delta

Fish survey IIlocabon(map ....) 2 31 5 6 9 1 1 12 14 | 17 19 22

Fish

Amblyrbynchichthys spAnabas testudineus s b _ bsCatlocarpio siamenstsChanda sp I P _

Cirrhinus thinnoides = = _ -= _ -_Cifrhinussp s__ scaas __ __ b P s Clarias batrachus _ s _ _ +_ _ _ _ _Chnam marocephalus s________Conica Sp 1 1 _P _ _ _ _ _ _ _Cosffnochilus sp _ _ _ e bCyclocheilichtrys enodos s _ s I I Cynodossus linr vaEkeucheranema tetradactylum = = = = -=Fluta alba s _Gksogobius giuris s _s DHampala macroiepdota eHypothaimchthys molitrix sllkha s--D - -lihSD_ _ ___ __ _ _- Latus carifer b - _. = _ b |_Leptobaibus hoevenji _____|__ L e lMastacembulus sp s I Morulius sp _ _ s __Mugilcep uI!s P _s

Mystus Sp s I D D b sMvstus wvckt I sNotopterus notopterus _ b sOphicephalusmicro ites - -4- rI I -_Ophicephalusstuiatus s SOsphronemus gourami L_I _._ I .Osteochilus _I - - - .Is

Oxele marsTlorata | s | -

Pangasius bocourb L I s 1 L_ _Paiiasius samensisPangasius spp p bPlotosus canrius I SIPII I! _Pogonogobius __I___ b IPoivremussp IS!Pnstokeps fascatus _IsIPseudocaena sp _4 _

Pungitius gonioitus-- s e L -t

Puntiodites proctorysronPuntius gononots 1p s sPuntus leiacanthus IsPuntzuss -S- p1:: - L -- F

Rasbora sp _ ._ . .. . _I_LTradtu russp -_ _ p s _ S - -TridiogasrS .*_.-- -}- - ---l- -4-- -- F- 1

1Oi 116 14 6 10 9 58 4 t O8 _ 7 j 4 7

production } d u d i d i d |u ri d dd

Shrimp _ . I ____|_|_ ____

1-35

Table 1.16: Aquatic life reported in the waterways of the Mekong Delta(cont)

Macrobrachium rosenberg i s Ta p j. P s -I - IMacrobrachium morabile S I _Maaobrachium equdens s sMetapenaeus ensis s I PMacrobrachium mammilodactylus s _Caridoma sp_ _ _ _ _ _ _ _ _ P _ _Metapenaeus sp _ P PPenaeus monodon -

Penaeus merguensisMacrobrachium lanchesteri -_ _ j - -_Caridina sp -- Macrobrachium sp sshnmps 1 I - -- Crab

Scy#a serrata P1_ _ _ _ s _ | isommanIathelphusaSP Q_ _P_ IPcrab p f __ P P I -

Shellfish II -r

Corbicuiaso sp - - -

Solensp I shellfish _ _ _ _ _2 'L. L PA

js=- present but smaler -- -- -- - t--b = present but r biggI?= present __ f __ . *e = disapeared L _1 _ _ _ _ L r~__ _ .__ - _ -- -I _ . __ -_...l._L _

u = catch unchanged _ f 1_ IL.ILi.i. - -=cath increased L - l I il - - i

1d = catch dereaed f

1-36

N

CAMBODIA

T H A I L~ ~~ ~~~~~~~ANDLAM

-~~~~o.~Figure 1 Locatio map of sampling (fishery surey)

GUL OFTHAILANDoh

Figure I1.08: Location map of sampling (fishery survey)

1-37

c) Macro Fauna

1.74 In order to gain insight into the composition of macro fauna on thecanal bed, a survey was carried out at 12 stations throughout the canals. APetersen grab sampler was used. The grab opening was 1 5 - 20 cm (300 cm2 ).For each sample 2 grabs were taken (600 cm2 ). At every station, 3 samples of600 cm2 each were taken. The Petersen grab takes samples up to a maximum of10 cm below the surface of the sediment layer. The samples were washedthrough a copper sieve with a mesh size of 0.5 mm. The organisms were collectedand preserved in formaldehyde 4%. The samples were analysed within 2 weeks.

1.75 The results of the sampling in an acid and non acid sampling stationare as presented in Tables 1.17 and 1 .18.

Table 1.17: Macro fauna species and their number at sampling station No. 19

MACRO FAUNA INDIVIDUALISAMPLE AVERAGE DENSITYSPECIES i . (individuall600 cm2)

Sam. 19.1 Sam.19.2 Sam.19.3

ANNELIDA

Oligochaete

Limnodrilus 1 43 14.3hoffmeisteri

ARTHROPODA

Insecta

Ubellulidae

Canacria sp 1 0.3

Total: 14.7

1.76 The results indicate a relationship between salinity and the numberof species in the samples. In the more salty/brackish waters a lower number ofspecies were found than was expected, especially in the Xa No east and the LapVo Sa Dec canal. In the Rach Soi - Hau Giang canal the species compositionindicates some influence of salt water to i 12 km west of Cai San.

1.77 Due to the shape of the Petersen grab the larger macro fauna whichlive deeper in the sediments could not be sampled. There are also largedifferences between the samples taken at the same location. This indicates thatmore samples have to be taken at each station or that a larger sampler must betaken. In light of the above, some suggestions have been given for the proposedmonitoring programme. In future, indicator species for salinity, type of sedimentand, if possible, acid have to be selected.

1-38

Table 1.18: Macro fauna species and their number at sampling station No.17

MACRO FAUNA INDIVIDUAL/SAMPLE AVERAGE DENSITYSPECIES lindividuall600 cm2)

Sam. 14.1 Sam. 14.2 Sam. 14.3

ANNELIDA

Polychaete

Lumbrinereidae

Lumbrinereis sp 1 0.3

Sabellidae

Sabellastate sp 1 0.3

Nephthydidae

Nephthys sp 17 9 29 18.3

MOLLUSCA

Bivalvia

Corbiculidae

Corbicula castanea 5 4 23 10.3

Corbicula cyrenformis 9 2 7 6.0

Corbicula moreletiana 1 6 7 4.7

Pisidiae

Afropisidium clarkeria 112 101 238 150.3

Mytiliidae

Limnoperna siamensis 2 0.7

ARTHROPODA

Amphipoda

Corophiidae

Corophium I 1 3 1.7homoceratum

Corophium japonocus 1 1 0.7

Kamaka sp 5 1.7

Apseudidae 1 0.3

INSECTA

Chironomidae

Corynoneura 216 316 266.0scutellata

Total: 461.7

1-39

1.78 The relatively low number of species and the low numbers of thespecies present in some of the samples is strange. If not due to sampling errors,it may be caused by the predation of fish and other animals, however, the fishstock does seems to be (very) low. It may also indicate that there are otherinfluences such as high concentrations of pesticides. In future, this has to betaken into account when conducting the monitoring programme.

d) Wildlife

1.79 During the field trip of 6 days only a few birds were seen, nomammals and almost no other animals such as reptiles were spotted, despite thespecial attention given to spotting wildlife. Only in some places frogs could beheard. However, on the markets along the waterways, an impression can beobtained of some of the water related biota that can be found in the area:

In the Ca Mau region the following species were observed:

1. Mammals: None.2. Birds on the market: Gallicrex cineria, Rallus stratus, Porzana

pusilla, Pophyrio porphyrio, Rostulabengalensis, Panadion haliaetus.

3. Birds in the field: Bubulcus ibis, Panadion haliaetus.4. Reptiles on the market: 5 (!) unidentified species of water snakes,

Cuora amboniensis, Trionyx cartilayineus

In the Rach Gia region the following species were observed:

1. Birds on the market: Gallicrex cineria, Bubulcus ibis, Callinulachloropus.

2. Birds in the field: Bubulcus ibis, Panadion haliaetus.3. Reptiles on the market: 2 species of water snakes, Cuora amboniensis.

1.80 This only gives certainty that these species are still present in theregion. The outcome of interviews made with several street vendors was that allthese animals were caught in the hinterland, smaller waters but not in the canals.More information of the wild flora and fauna present or thought to be present inthe Ca Mau peninsular and the mangrove region can be found in the report of the'Coastal Wetlands Protection and Development Project'.

1.81 It is obvious that aquatic species like fish and shrimps and otheredible organisms suffer as severe over fishing by all possible ways of fishing, bythe use of pesticides and lack of suitable habitat.

1-40

2. IMPACTS ON WATER QUALITY AND ECOSYSTEMS

2.01 The impact assessment for water quality is to be made in relationwith the medium and long term impacts, that is to say, the acidity and salinity ofthe water bodies influenced by the waterways that will be improved. Pollution bynutrients, pesticides have only some indirect relation with dredging operations.Short term impacts on water quality are merely related to the disturbance and re-suspension of (polluted) sediments during the dredging operations.

2.02 Impacts of the improvement works in the main waterways on thewater quality system are essentially related to:

- short term impacts due to dredging operations;- short to medium term impacts due to the oxidation of acid sulphate soils;- long term impacts due to hydraulic conditions and salinity intrusion;- impacts due to changed use of the waterways, including operational

pollution and pollution arising from accidents.

A. Short Term Impacts

2.03 Water turbidity will increase during dredging, especially when thedredging spillage (material which is excavated but not picked up by the dredger)is not kept to a minimum. This could affect fish populations of aquatic organismsand could render the water temporarily unsuitable for domestic uses. Fish speciesshould be allowed to migrate to canal stretches where dredging has not yetstarted. Dredging should preferably be carried out in upstream direction in orderto provide an escape route for fresh water species, which otherwise are graduallypushed into saline water, or are trapped in highly turbid waters. If there are lateralcanals or creeks available within relatively short distances to which fish canmigrate or escape, the dredging direction will become less important (from anenvironmental view point),

2.04 In general there will be less negative impacts by using a grab dredgeinstead of a cutter dredge, as the structure of the dredge clay will be lessdisturbed. In order to obtain a better insight into the release of acid from acidsulphate soils as a result of the use of cutter dredgers instead of grab dredger,laboratory tests were performed. It was found that the release of acid onlybecomes significant after a few days which will be after most transport water hasdrained from the deposition site. Consequently the use of cutter dredger as analternative for grab dredger can be accepted.

2.05 Excavation of the bank slope and bottom means the destruction ofbiota present on and in these habitats. Colonisation and succession of the softbottom macro fauna community has to start from the beginning. Excavation ofboth banks could affect (commercial) fish stocks, and other edible biotaconsiderably. In order to reduce this impact (and at acceptable costs), thewidening should preferably take place at one bank only.:

1-41

2.06 If the canal is widened on one side only, one bank will remainuntouched and the biota will still be able to find suitable habitats. Although acertain decrease of biota can be expected, this will be much less in comparisonto widening on both sides. Since there are many settlements along the canalsthere is little room for natural biota. Widening one side means continuing thestatus quo on the other bank. There are however, stretches of waterways with farfewer settlements of people on one bank. This is found along the Rach Soi - HauGiang Canal and the Rach Gia - Ha Tien canal where more (natural) biota is foundthan on the other less occupied bank. From an ecological point of view, it is notrecommended to dredge the bank representing the most ecological values.

The Rach Gia - Ha Tien canal is the only stretch of waterway in which brackishand sea water species are found in any large numbers. In other parts of thewaterways the brackish and sea water species can not survive long in the freshwater conditions. These canals are directly connected to the sea by at least fivelateral canals which provide excellent passages to salt water and shelter fromdredging operations.

B. Medium Term Impacts

2.07 The medium term environmental impact is closely related to thedredging of potentially acid sediments and the release of acid and metal ions in thewaterways and the fields during a number of years following the implementationof the project. The magnitude of the impact is related to:

- the volume of acid sediment to be dredged and total potential acidity;- the dimensions of the deposit sites and the possibilities to cover the

disposal sites;- the acid run-off from the dredge material deposit in relation to the acid run-

off from surrounding fields.

These parameter have been determined and will be described further in the nextparagraphs.

Estimated Quantity of Potentially Acid Soil to be dredged

2.08 The quantities of potentially acid sediments which will be excavateddepend on the depth of occurrence and thickness of the potentially acid layers(pyritic layers) and the required canal dimensions. Based on the results of the soilsurvey, cross-sections of the existing canal dimensions at 100 meter interval andrequired canal dimensions. Computations have been made of the total dredgingarea in m2 and the dredging area consisting of potentially acid sediment in m2 foreach cross-section. The total cross-sectional area to be dredged and the areaconsisting of potentially acid sediment were multiplied with the distance for therepresentative canal distance (usually 80-120 m.) and accumulated for the entirecanal.

1-42

In order to visualize the location of the potentially acid sediments in the cross-sections a number of representative cross-sections were presented. The followingvolumes were prepared:

- List of dredging and pyritic volume Cay Nhat creek- List of dredging and pyritic volume That Thu Ganh Hao river- List of Dredging and pyritic volume Rach Gia Ha Tien canal.- List of dredging and pyritic volume Xa No canal- List of dredging and pyritic volume Tat Cay Tram canal- List of dredging and pyritic volume Trem Canh Den canal- List of dredging and pyritic volume Lap Vo Sa Dec canal- List of dredging and pyritic volume Rach Soi Hau Giang canal

2.09 The total amount of potential acidity of the pyritic sediments to bedredged can be derived from the results of the physical and chemical analysis ofthe soil samples presented in Table 2.01.

Table 2.01 : Volume & potential acidity of potentially acid soils to be dredged

canal! cross- Length pot. acid totaL perc. TPAsection canal dredging dredging

stretch volume volumem. 1000 m3 1000 m3 1000 mol(+)

xa NO L; uZ a YvU U UC4 12088. 474 1023 46 203873r5 3144 38 186 21 48902

Tat Cay tram C6 4236 71 272 26 101365

Tram Canh Den C7 0 0 0C8 33205 1564 3021 52 378136C9 0 0 0

Lap Vo-Sa Dec C12 38898 361 744 49 187981

Rach Soi-Hau Giang C13 12193 8 200 4 1894C14 12631 0 635 0 0C15 8806 0 473 0 0C16 12152 0 521 0 0C17 7982 0 189 0 0

Rach Gia-Ha Tien C18 6626 144 246 59 2069C19 12394 542 559 97 746058C20 13938 652 766 85 939872C21 11443 357 575 62 474263C22 9137 321 469 68 227080C23 9096 68 357 18 36119

these volumes correspond with a canal width of 30 m at the bottom andno overdredging.

2.10 The calculation of the total dredging volumes and volumes of pyriticsediment to be dredged indicate that the largest amounts of pyritic sediments tobe dredged are located in the Tram Canh Den canal and Rach Gia to Ha Tien canal.The calculations indicate that in large sections of the Rach Gia - Ha Tien canal themajor part of the sediment to be dredged consists of pyritic sediments.

2.11 The calculations presented in Table 2.01 also indicate that the soilto be dredged in the Rach Gia - Ha Tien canal contain the largest amount ofpotential acidity. The soil to be dredged in the Xa No, Tat Cay Tram, Tram CanhDen and Lap Vo Sa Dec canal contain smaller amounts of potential acidity.

1-43

2.12 Experience obtained in the Delta, indicates that during the dryseason acid water is transported by capillary movement to the surface of thedredge spoil and the surface of cracks formed in the clayey sediment. The acidityis precipitated at these surfaces as white and brown Al and Fe-salts, mainlysulphates (ref. 8,9). During the first months of the rainy season, the acidityaccumulated at these surfaces is washed into the canals and neighbouring fields.Acidity washed into the canals may cause massive starvation of fish, shrimps orcrabs in the canal or river/estuarine/coastal seas receiving acid drainage waterfrom the canal (ref 10,11,12). Little is known on the effect of acid run-off fromdredge spoils on the yield in rice fields adjacent to the spoil. Little effect isexpected in land consisting of raised beds.

2.1 3 The envisaged widening of existing waterways will undoubtedlyresult in acidification in stretches where these canals cut through potentially acidsediments. The effect of the inflow of acidity into the canals and adjacent fieldswill be evaluated in the context of the acidifying effect of the landuse and soiltypes along the canals (ref 13). Therefore the acidifying effect of different formsof landuse on different soil types has been quantified.

Acid Run-Off from Dredge Spoil

2.14 The potential acidity contained in the spoil is not immediatelyreleased to the environment. Some spoils may still contain most potential aciditywithin the inner core of the spoil for many years. This phenomenon can beexplained by the fact that the pyritic sediments in the Mekong Delta consist ofclays and silty clays of heavy to very heavy texture. Oxidation of pyrite within thespoil is strongly hampered by the slow rate of oxygen diffusion into the spoil.Secondly, once pyrite has been oxidised, diffusion of the acid end-products ofpyrite oxidation to the surface of the spoil is equally slow. In the heavy claystransport of acid end-products of pyrite oxidation such as H+, Fe2 , Fe3", Al3 + andso,2 mainly takes place by mass-flow during capillary rise of soil moisture duringthe dry season or dry spells during the early rainy season. Once the acid end-products reach the soil surface they precipitate as acid salts. These acid salts aredissolved by rainfall and washed either into the canal or into the fields behind thespoil as acid run-off.

2.1 5 The determination of the concentration of the run-off from raisedbeds or dikes is a very difficult issue. The overall process can be divided in thefollowing sub-processes:

step 1: oxidation of Pyrite in the raised bed or dike;step 2: diffusion of acidity through capillary rise to the surface of

the raised bed or dike;step 3: washing the acidity from the dikes by rainfall.

2.16 Quantification of these processes is very difficult in view of the largeamount of unknown parameters. A simplified approach has therefore been usedto estimate the amount of acid run-off from the dredge spoils. For details on thecalculation, reference is made to Annex 11-3.

1-44

2.17 The surface of the spoil exposed to rainfall is a very importantparameter to determine the amount of run-off from the spoil. When for instancean amount of 100 m3/m of pyritic sediment is simply sprayed on the land allowingit to spread out evenly, the thickness of the spoil may be as thin as 20 cm. Thesurface of this spoil exposed to rainfall is 500 m2/m. When the spoil is keptbetween bunds of 1 .0 m height, the surface of the spoil is reduced to about 100m. resulting in an amount of 20% of the run-off of the spoil without bunds. Whenthe height of the bunds is increased to 2 m, the surface of the spoil is furtherreduced to about 50 m and run-off is further reduced to 10% of the run-off of aspoil without bunds.

2.18 Table 2.02 shows the calculation of the acid run-off from the dredgespoil for the following cases:

- no bunds, the height of the spoil (H) is 0.2 m.- construction of bunds, H = 1 m.- construction of bunds, H = 2 m.

Table 2.02 : Estimated annual acid run-off from pyritic dredge spoils

canal; pro. lIgth total both total surface surface surace eat. est. acid acid acidcanal dredging P-layers dredging spoil spoil spoil run-aff conc run-eff run-off run-off

stretch volume drdging voluee 1-0.2 *. H-i1 .X -2 a. run-off H-0.2 * H-I e 92 *.

m. 000 *3 1000 S *3/e *2/m ut/r *2/r m/year l()/3 ol(+)/3 l(+)/ rol(t)/r

Cho 6as ti

Rang Thit CU

Xl o C3 23923 904 0 38 189 36 19 0M662 0 0 0 0C4 12iM 3023 474 es 423 as 42 0.4625 40 11217 2243 3122CS 3144 1I6 38 S9 296 59 30 0.6625 60 11747 2349 1175

Tat Cay trae C6 4236 272 71 64 321 64 32 0.4625 60 12760 2552 1276

ram Canh Dan C7 0 0 0 0 0 0 0 0.662S 60 0 0 0CB 33205 3021 1564 91 4 91 4S 0.6625 60 1802 3616 3806C9 0 0 0. 0 0 0 0 0.6625 30 0 0 0

Lap Wo-Sa Dec C12 3898 744 361 19 f 19 la 0.6625 40 2533 507 253

Hach Soi-hau Siang CL3 12193 200 a 16 82 16 8 0.6625 20 1086 21 109C14 12631 635 0 S0 252 S0 25 0.662 0 0 0 0CiS 8806 473 0 4 Z69 4 27 0.6625 0 0 0 0C16 12152 521 0 43 218 43 21 0.6625 0 0 0 0C17 7962 189 0 24 1li 24 12 0.662S 0 0 0 0

Rath Gia-ha Tien CUS 6626 246 144 37 IsS 37 19 O.62 40 4910 962 491C19 12394 559 842 45 22 40 23 0.6625 60 8989 1792 896Ci2 13938 766 652 8 275 45 27 0.6625 66 10920 2184 1092C21 11443 078 357 80 281 so0 20.62 60 9984 1997 998C22 9137 469 321 Si 256 S1 26 0.6625 00 6496 1699 850CZ3 9096 387 68 43 213 43 21 0.6625 40 5633 1127 563

2.19 The estimation of the yearly amount of acidity washed from thedredge spoils in the canal stretches is presented in Table 2.02 and shows that thelargest amount of acidity is being released in the Rach Gia - Ha Tien canal.Considerable amounts of acidity are being released in the Xa No, Tat Cay Tramand Tram Canh Den canals.

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2.20 The amount of acid run-off can be strongly reduced by covering theacid sediment by non-acid sediments in those canal stretches where below thepotentially acid sediments a non-potentially acid sediment is found at shallowdepth. This is the case in most parts of the Mekong Delta. In these area's thepotentially acid sediment consists of moderate to severely potentially acid grey todark grey (sometimes black) heavy clay. The underlying non-potentially acidsediment usually consists of grey to very grey sandy or silty clay. The lightertexture can be explained by the fact that this sediment has been deposited undermore turbulent marine or estuarine conditions. This situation is encountered in theXa No, Tat Cay Tram, Tram Canh Den and Lap Vo Sa Dec canals.

2.21 The potentially acid sediments in the Ha Tien Rectangular weredeposited in an earlier stage of Delta development. The thickness of the sedimentsis usually more than the above mentioned sediments: 3 - 6 m. Below thepotentially acid sediments, an old alluvial sediment is found of pleistocene age.The potentially acid sediments consist here of moderately to severely potentiallyacid grey to very grey (sometimes black) heavy clays. The underlying old alluviumconsists of light grey to grey heavy clay, usually with a very low organic contentand greater shear strength compared to the darker, softer and more organicpotentially acid sediment.

2.22 If care is taken to remove the potentially acid sediment first andthen the underlying non-potentially acid sediment are removed and used to cap theacid sediments, a strong reduction of the acid run-off can be achieved. Asexplained above, the potentially acid and non-potentially acid sediments can bedistinguished by colour, texture and firmness. During the process of dredging thepotential acidity of the different sediments can easily be checked using the quickoxidation test mentioned Annex 11-3 (Chapter 2).

2.23 An evaluation has been made of the possibility to cover thepotentially acid sediment with non-potentially acid sediment based on the cross-sections. The results are shown in Table 2.03.

2.24 The evaluation of the possibilities as shown in Table 2.03 indicatesreasonable and good possibilities in the Xa No, Tat Cay Tram and Tram Canh Dencanals. The non-potentially acid sediment in the Lap Vo Sa Dec canal is locatedbelow the projected canal bottom and will therefore not become available to coverthe potentially acid sediment. Locally, where the non-acid layer is found atshallower depth covering may be possible. As expected, the thickness of thepotentially acid sediment in the Rach Gia - ha Tien canal is such that covering isnot possible. In the north-western part of the canal (cross-sections C21, C22 andC23) the old alluvial may be found at such depth that covering could be an option.

Canal Pro. Total P1 P2 NP top NP bott. Perc. Effectivenessdredging area area area area NP bott Iarea 0m

2m

2m

2m

2m

2%

Cha Gao Cl 0,oU

Mang Thit C2 c|)

Xa No C3 _.C4 100.35 43.55 0 33.63 23.18 23 reasonable CD

C5 'C5 87.85 19.77 0 16.8 51.28 58 good '-4

Tat Cay Tram C6 85.21 22.28 0 38.8 24.13 28 reasonable <CDCDTram Canh Den C7 -0

C8 51.13 8.84 0 31.75 10.54 21 reasonable |4CDC9 I

'4Lap Vo-sa Dec C12 not possible, the non-pyritic layer lies just

below the required bottom a)

Rach Soil-au C13 good Q-LOGiang C14 CD

C16 CDC17

RI ch Gia-Ha cis not possible, pyriticla yer_untilrequiredbottom CRach Gia-Ha C18 not possible, pyritic layer until required bottomTien C19 not possible, pyritic layer until required bottom e

C20 not possible, pyritic layer until required bottom C21 reasonable oC22 not possible, pyritic layer until required bottom p

C23 56.83 10.62 0 33.8 12.41 22 reasonable o

CDl~ ~ ~ ~ ~ ~ __ =__ .__ .___ ___ _______________ _

0)4

< 0)

1-47

2.25 When the potentially acid sediment is well covered with non-potentially acid sediment, both the diffusion of oxygen into the spoil as well as thecapillary rise of acid end-products to the soil surface are greatly reduced. In orderto estimate the run-off in a well constructed spoil the following reduction factorsof the surface of the spoil exposed to rainfall have been assumed:

Possibility to reductioncover the spoil: factor:

good 0.2reasonable 0.5not possible 1.0

2.26 Table 2.04 shows the estimated run-off of acid water from spoilsin which care has been taken to cover the potentially acid sediment with non-potentially acid sediment. The results presented in Table 2.04 indicate that acidrun-off can be strongly reduced in the Xa No, Tat Cay Tram and Tram Canh Dencanal.

Table 2.04 : Yearly acid run-off from dredge spoils in which potentially acidsediment has been covered with underlying non-potentially acid sediment.

canal: pro. length total both total surface surface surface *sti.atedestimated acid acid acidcanal dredging P-layers dredging spoil spoil spoil run-off conc. run-off run-off run-off

stretch volum dredging volur e-0.2 a. -1 r. H-2 *. run-off h-0.2 r 9-1 a 1-2 S.volume

*. 1000 *3 1000 *3 *3/s 02/r 2/u *2/rn a/year mol(+)/ 3 ol(i)/il(.e)/m l(+)/rn

1a is C3 23923 904 0 38 189 38 19 0.6625 0 a 0 OC4 1208B 1023 474 85 212 42 21 0.6625 40 5609 1122 561

CS 3144 11 38 59 9 12 60.66 60 2349 470 Z3

Tat Cay tram CS 4236 272 71 64 161 32 16 0.6625 60 6360 1276 638

Tra Canh Dn t7 0 0 0 0 a 0 0 0.6625 60 0 0 0CB 33205 3021 1564 91 227 45 23 0.6625 60 9041 1606 104C9 0 0 0 0 0 0 00.6625 30 0 0 0

Lip Vo-Sa Dec C12 38681 744 361 19 96 19 10 0.6625 40 2533 507 253

Rach Soi-Hau Giang C13 12193 200 a 16 a 2 1 0.6625 20 109 22 11C14 12631 635 - 0 50 0 0 0 0.6625 0 0 0 0cis 8805 473 -0 54 0 0 a 0.6625 0 0 0 0C16 12152 521 0 43 0 0 0 0.6625 0 0 0 0Cl7 7962 189 0 24 0 0 0 0.6625 0 0 0 0

Rach Gia-Ha Tien CIS 6626 246 144 37 135 37 19 0.6625 40 4910 982 491C19 12394 559 542 45 225 45 23 0.6625 60 6959 1792 896C20 13938 766 662 55 275 SS 27 0.6625 60 10920 2184 1092C21 11443 575 357 50 126 25 13 0.6625 60 4992 998 499C22 9137 469 321 53 256 51 26 0.6625 50 8496 1699 850C23 9096 387 68 43 106 21 11 0.6625 40 2616 563 262

2.27 Covering potentially acid sediment with non-potentially acid reducesthe yearly acid run-off. The potential acidity is maintained in the spoil for a longerperiod. Table 2.05 shows the calculation of the period until complete depletion ofthe acidity present in the spoil. The period of depletion is presented for thefollowing 6 cases:

case 0: without case, no bunds, H = 0.2 m., no coveringcase 1: no bunds, H = 0.2 m., coveringcase 2: low bunds, H = 1.0 m., no coveringcase 3: low bunds, H = 1.0 m., coveringcase 4: high bunds, H = 2.0 m., no coveringcase 5: high bunds, H = 2.0 m., covering

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Table 2.05 Period until depletion of the potential acidity of the spoil.

canal: Case Number0 1 2 3 4 5

year year year year year year

Cho Gao, C1Mang Thit, C2 - -

Xa No, C3 0 - 0 - 0 -

C4 2 3 8 15 15 30C5 1 7 7 33 13 66

Tat Cay Tram C6 2 4 9 19 19 38Tram Canh Den C7 - - - - - -

C8 1 1 3 6 6 13C9 - - - - -

Lap Vo-Sa Dec C12 2 10 10 19 19 -

Rach Soi-Hau GiangC13 0 1 1 7 1 14C14 0 - 0 - 0C15 0 - 0 - 0 -C16 0 0 - 0 -

C17 0 - 0 - 0

Rach Gia-Ha TienCl 0 - 0 - 1 -

C19 7 7 34 34 67 67C20 6 6 31 31 62 62C21 4 8 21 42 42 83C22 3 3 15 15 29 29C23 1 1 4 7 7 14

Resulting Changes in Acid Run-Off

2.28 The impact of yearly acid run-off from the dredge spoil on water andland should be evaluated in relation to the yearly acid run-off from the landbordering the canals. When for instance, the canal cuts through an area withsevere actual acid sulphate soils (Sjl) which is used for the cultivation ofeucalyptus or pineapple on raised beds, the yearly acid run-off from the land isusually such that the pH of the canal water at the start of the rainy season is inthe range of 2.8-3.5. Even substantial additional acid run-off from dredge spoilsmay result to a drop in pH of 0.1 unit only. When however a canal cuts throughan area where potentially acid sulphate soils are limited to the subsoil and the landis used for rice cultivation, pH of the surface water may be close to neutral (6-8).The acid run-off from a dredge spoil may result in pH values in the range of 3.5 -4.0, a drop of 2 - 4.5 pH units.

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2.29 The method to estimate yearly acid run-off from fields bordering thecanal is described in Annex 11-3. The results are presented in Table 2.06.

Table 2.06: Calculation of the annual acid run-off from land bordering the canals.

RltE: 7ISEiiD BEOS:

canal: pro.land use: soil type: width period perc. conu, acid est. surface cone. acidof of rate ground- ,run- acid raised run-off acid

rice raised strip pert. water off run-off bedsbeds no ass mod severe factor

S S 5 1 t *. days v/day lol(+)/23 mol(+)/r u/year 1/M Ml(+)/1m o m(I)/(+

Cho Gao Ci 0 100 100 0 0 0.00 8C0 180 0.00015 0 0 0.8 0 0 0

Pang Thit C2 90 10 0 80 20 0.60 800 180 0.00015 24 518.4 0.8 36 0 467

Xa No C3 90 10 100 0 a 0.00 800 1800.00015 0 00.6625 0.8 to 0 0C4 90 10 100 0 0 0.00 B00 180 0.00015 0 0 0.6625 0.8 0 0 0Cs 80 10 20 0 go 0.80 80O 180 0.00015 32 691.2 0.6625 0.8 48 20352 2657

Tat Cay tram C6 S0 50 .0 0 100 I.00 800 180 0.00015 0 0 0.6625 0.0 60 25440 ;2720

Tram Canh Den C7 75 25 0 sO 20 0.60 800 180 0.OOOIS 24 518.4 0.6625 0.8 36 15264 6205C8 90 10 0 80 20 0.60 8C0 180 0.00015 24 S58.4 0.6625 0.8 36 15264 1993C9 90 10 0 80 20 0.60 800 180 0.000 C 24 518.4 0.6625 0.8 36 15264 0993

Lap Vo-Sa Dec C12 so 20 80 10 0 0.05 8O 180 0.00015 2 43.2 0.6625 0.8 3 1272 289

RLch Soi-hiu Giang C13 90 10 100 0 0 0.00 Bo0 1 O 0.00016 0 0 0.6625 0.8 q 0 0014 90 10 S0 50 0 0.25 800 180 0.00C15 10 216 0.6625 0.8 1I 6360 330CIS 90 10 0 100 0 0.50 800 180 0.00015 20 432 0.6625 0.8 3. 12720 1661C16 90 10 SO 50 0 0.25 8OO 180 0.00015 10 216 0.6625 0.8 IS 6360 830C17 90 10 100 0 0 0.00 O 1800.00015 0 0 0.6625 0.8 0 0 0

Rach Cia-Ha Tien CI8 90 10 100 0 0 0.06 800 180 O.0O015 0 0 0.6625 0.8 0 0 0C19 90 10 0 SO S0 0.75 800 180 0.00015 30 648 0.6625 0.8 45 19080 2491020 80 10 0 50 50 0.75 800 180 0.00015 30 648 0.6625 0.8 45 19080 2491C21 0 100 0 50 50 0.75 800 180 0.00015 30 648 0.6625 0.8 45 19080 19080C22 80 20 0 50 50 0.75 80O I18 0.00015 30 648 0.6625 0.8 45 19080 4334C23 0 40 20 40 40 0.70 Wu ISO 0.00015 28 604.8 1.6625 0.8 42 17808 7123

2.30 According to the calculations presented in Table 2.06, very highamounts of acid run-off are found in cross-section C6 in the Tat Cay Tram canaland cross-section C21 in the Rach Gia - Ha Tien canal. The high values are causedby the fact that the land use consists for a large part of raised beds on partlysevere, partly moderately acid sulphate soils.

2.31 Table 2.07 presents the yearly acid run-off from dredge spoils as apercentage of the acid run-off from bordering land, under the 6 cases mentionedbefore:

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Table 2.07: Yearly acid run-off from the spoil and effect of mitigating measures.

0 1 2 3 4 5canal: pro. acid acid acid acid acid acid

run-off run-off run-off run-off run-off run-offH=0.2 m H=0.2 m H=1 m H=1 m H=2 m H=2 m.

mol(+)/m mol(+)/m mol(+)/m mol(+)/m mol(+)/m mol(.+ )/m

Xa No C3 0 0 0 0 0 0C4 11217 5609 2243 1122 1122 561C5 11747 2349 2349 470 1175 235

Tat Cay tram C6 12760 6380 2552 1276 1276 638

Tram Canh Den C7 0 0 0 0 0 0C8 18082 9041 3616 1808 1808 904C9 0 0 0 0 0 0

Lap Vo-Sa Oec C12 2533 2533 507 507 253 253

Rach Soi-HauGiang C13 1088 109 218 22 109 11

C14 0 0 0 0 0 0C15 0 0 0 0 0 0C16 0 0 0 0 0 0C17 0 0 0 0 0 0

Rach Gia-Ha Tien C18 4910 4910 982 982 491 491C19 8959 8959 1792 1792 896 896C20 10920 10920 2184 2184 1092 1092C21 9984 4992 1997 998 998 499C22 8496 8496 1699 1699 850 850C23 5633 2816 1127 563 563 282

2.32 Table 2.08 presents the acid run-off from dredge spoils as apercentage of the acid run-off from the neighbouring fields and the recommendedmitigating measures to be taken in the various canal stretches are underlined.

Table 2.08: Yearly acid run-off from dredge spoils as a percentage of the yearlyacid run-off from the bordering lands.

case: 0 1 2 3 4 5canal: profile % % % % % %

Cho Gao C1 - - -

Mang Thit C2 0 0 0 0 0 0Xa No C3 - .

C4 - -

C5 442 88 88 18 44 9Tat Cay tram C6 100 50 20 10 10 5Tram Canh Den C7

Cs 907 454 181 91 91 45C9 . - _

Lap Vo-Sa Dec C12 877 877 175 175 88 88Rach Soi-HauGiang C13 - - - -

C14 0 0 0 0 0 0C1S 0 0 0 0 0 0C16 0 0 0 0 0 0C17 -

Rach Gia-HaTien Cis - . . .

C19 360 360 72 72 36 36C20 438 438 88 88 44 44C21 52 26 10 5 5 3C22 196 196 39 39 20 20C23 79 40 16 a 8 4

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C. Long Term Impacts

a) Salt Intrusion

2.33 Salt intrusion causes problems for agriculture (especially during thedry season) and reduces the possibility to use the water for other (household)purposes. Some increase in salt intrusion due to the growing demand for freshwater could be expected. Widening and deepening of the waterways will not resultin a significant increase in salt intrusion. Modelling results show that the isohalineof 1 g/l and 4 g/l will not be affected.

2.34 The construction of sluice gates as foreseen for the Ca MauPeninsular as part of a salinity mitigation project, are under implementation andwill affect the salinity intrusion in the Xa No and the Chac Bang canals and theconnecting water bodies.

2.35 Sluices interrupt free migrating routes for aquatic organisms like fishand shrimps which use the brackish environment to complete their life cycle. Thiswill affect some of the commercially important marine shrimp species, and also theGiant fresh water prawn. This species needs brackish water for its larval stage anddevelopment. Therefore sluices or any salinity control works will have a negativeimpact on the aquatic ecosystem in the south east regions of the Delta.

2.36 There is another danger related to the prevention of salinityintrusion. The breeding conditions for the fresh water vectors such as malaria willincrease. It should be appreciated that there could be an increase in malariaalthough it is not certain that this will happen.

b) Tidal Movements

2.37 The widening of the canals will result in the movement of a greateramount of water in and out the canals and connecting river stretches due to tidalmovements. This means that higher water velocities could occur in the waterwaysthan in the existing situation.

2.38 Higher velocities implies some more erosion and an increase intransport of sediments. This may affect flora and fauna present along the banksof the water bodies and also the people living on those banks. Faster watermovement means a better distribution of waste and a quicker discharge of pollutedwater. It may be expected that this will have a favourable influence on the waterquality. There may be some changes in the aquatic ecosystems but these will notbe unfavourable. Most of the water related biota in the waterways is used tochanges in water conditions as caused by water velocities. These changes are notexpected to cause measurable changes in the aquatic ecosystems.

2.39 If it is necessary to protect the banks of certain stretches with toprevent erosion it may have an influence on aquatic live. If the means ofprotection preclude the growth of vegetation this must be regarded as negative.If the use of material cannot be avoided it is recommended to use rip-rap of stiffclay or rockinstead of wood or steel sheet piles. Wood and steel create an abrupt borderwhich eliminates the conditions necessary for many organisms to maintainthemselves.

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D. Impact due to changed use of the waterways

a) Resettlement

2.40 In general in can be stated that the resettlement could be a positiveimpact on the natural environment. Canal water pollution in populated areas in theMekong Delta is significant. The main pollutants are organic matter, nutrients andpathogens from domestic wastes, discharged directly into the water. Withcontinuing human encroachment including latrines and animal cages constructedabove canals, surface water pollution is expected to increase from year to year.Relocation of indiscriminate settlements at a distance from the former locationwould not only facilitate canal dredging and rural road construction along canalbanks, but would also allow for better control of water pollution (pit latrines,waste pits etc.).

2.41 In combination with the need of resettling the people living on thebanks, that will be dredged, new resettlement areas will be developed. A systemof dead ending canals could be dredged in a grid that is connected to thewaterway. The main concept is to dredge a main canal of a certain length anddredge some others perpendicular to the main one. In this way a moreconcentrated system of small waterways is developed along which the peoplesettled. They still live on the bank of a water body within the same community(same neighbours), while the benefits of concentrated settlements are achieved.It will be easier to organise waste collection and sewage treatment (latrine pits,in future sewage clearing installations), and in addition there will be also betteropportunities to provide the population of such a new village with a betterinfrastructure, a better drinking water system and other utilities.

2.42 The grid system must be connected to the water body or waterbodies in such a way that a maximal natural refreshment of the water is possible.If not, severe pollution problems may be expected as long as there are no sewagetreatment installations.

b) Interface of shio traffic and vessel construction

2.43 An increase in navigation will also give rise to other pollutants suchas oil and lubricants. At present, oil pollution is already noticeable along intensivelyused navigation routes.

2.44 Anti-fouling paints containing organo-tin compounds are dangerousto molluscs. It has been proved that the snail Nucella lapilus, which inhabits therocky coasts of Europe, is vulnerable to organo-tin compounds. There is a strongsuspicion that other molluscs will also be vulnerable to this. Nowadays the use ofthese anti fouling paints has been banned in some European countries. In general,no anti-fouling parts are used on vessels plying the waterways in the MekongDelta, because the vessels travel through salt, brackish and fresh water whichprevents the growing of an unacceptable mass of organisms on submerged partsof the vessels.

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c) Wood Preservation

2.45 Wood preservation by means of coal tar (carboleum) means therelease of poly aromatic hydro carbon chemicals which can cause cancer. Due tothis, the use of coal tar and especially carboleum in European countries may nolonger be used to prevent wooden materials from rotting. If possible the use ofthese preserving compounds must be avoided and be replaced by environmentallyfriendly alternatives like metallic oxide primers or epoxy paints.

2.46 The discharge of more natural products by ships will not be aprobiem when it is delivered to a central point, however, during the time that nosewage clearing installation is available, everything will be discharged to theaquatic environment. This is different for oil, oil rests , mixtures of oil and water(bilge water) and all other artificial hazardous pollutants. Near the bunker stations,there must be a possibility to store these pollutants. Legislation will have to bepassed to prevent any oil dumping.

2.47 If accidents happen with ships containing liquid fuel, pesticides orfertilisers severe negative impacts to the environment will be the result. A goodaids to navigation system can minimise these risks. Regulations will have to bedrawn up on the storage and transport of dangerous products.

2.48 With increased navigation on the waterways, bank erosion couldoccur due to ship induced waves. This bank erosion can be reduced by seeding orplanting vegetation along the banks. In locations where seeding and planting is notpossible (steep slopes), a flexible slope protection is a good alternative. This givesa stable slope and offers good possibilities for different biota to establish.

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3. ALTERNATIVES AND MITIGATING MEASURES

A. Alternative Project Designs

3.01 The alternative solutions to meet the project objectives are limited.In principle the zero option is there, while furthermore different routes and channeldimensions have been considered, during the preparation of the Feasibility StudyReport.

3.02 If the project were not to be implemented, the growing transportdemand would result in a gradual increase of the number of vessel movements onthe canals, until the maximum capacity had been reached. Due to the restrictedchannel dimensions a shift towards larger vessel sizes would not be stimulated,which in turn would lead to a higher fuel consumption, more boatman, mooringand servicing facilities along the waterways per DWT.Km and more difficulties inreducing the discharge of waste and pollutants from the vessels and shore basedservice facilities. At the same time there will be pressure to develop road transportto take care of the transport requirements, that can not be met by the inland watertransport facilities. Particularly in respect of fuel consumption and related airpollution such an option would be less attractive.

3.03 The alternative routings which were considered as part of theFeasibility Study, are all expected to have a similar impact on the environment andtherefore the final option was selected for economic reasons. From the previouschapters it may be clear, that the current ecological value of the canals and theirbanks has become rather insignificant due to over-fishing and the cultivation of thecanal banks.

3.04 The ecological value of alternative routes has not been investigated,but can hardly be expected to be significantly less. Also the quantity of potentialacid soils to be dredged, the most dominant environmental factor for the project,has not been explored for the alternative routes. As the starting position in Ho ChiMinh City and end positions of the waterways in the potential acid soil areas ofKien Luong and Ca Mau are the same for all alternative routes, the acidityproblems to be encountered along the alternative routes can be expected to be inthe same order of magnitude.

3.05 The width of the canals (bottom width and bank slope), will havea direct relationship with the acidity problems to be expected. As any reductionin width will also reduce the resettlement needs and dredging cost as a whole, thefinal option which was selected was derived from the minimum acceptable canalwidth and steepest stable slopes possible.

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B. Mitigating Measures

3.06 The impact of most changes resulting from the project, like changesin salinity, currents, pollution, resettlement, etc are rather limited or may even bepositive from an environmental point of view. The impact of rather negativeeffects like the destruction of most macro fauna and vegetation over large waterbottom and canal bank areas during capital dredging works, or the expectedincreased pollution by oil and fuel due to the increase of water transport could bereduced by applying one-sided canal widening and implementation of plantingschemes, or the introduction of centralized collection of lubricants and otherharmful ship waste.

3.07 The most dominant impact on water quality, the survival andrecovery of micro and macro fauna and commercial fish and crab populations inthe water and the agricultural production is related to the dredging and storage ofpotential acid soils.The alternative ways on land of dredging and storage will be discussed in the nextparagraph.

3.08 Mitigating measures, that could be applied during excavation are:

- Avoiding as much as possible the disturbance of the bottom material, thatis not directly removed by the dredger as this may lead to an increase ofsuspended (polluting) sediment and release of acid from the loosenedbottom material. When a dragline or grab crane is applied this can beachieved by restricting the depth of excavation and removing the materialin layers. The same restrictions should also be imposed when applying acutter dredger.Such restrictions will reduce the production and thusincrease the dredging cost. Therefore optimal but realistic working methodswill have to be described and proper supervision will have to take place inorder to ensure good results. Under such circumstances the impact of acutter dredger and a grab dredger will be comparable.

- The deposition of the dredged material creates the second and moredominant impact on the environment due to the release of acid and metalions to the waterways and surrounding fields.As shown in section 2.B considerable reductions in acid discharges can beachieved by reducing the area of the deposition site by applying contain-ment bunds and by covering the potential acid soil deposits by non acidsoils, while furthermore a cost effective approach could be achieved byaccepting a 20 % acidity increase when determining the required mitigativemeasures for the different stretches to be dredged.

3.09 Based on the calculations presented in chapters 2.B the followingmitigating measures need to be applied.

3.10 From a soil point of view, no special dredging precautions need tobe taken in the Cho Gao canal, Mang Thit canal, north-eastern and central part ofthe Xa No canal, Rach Soi - Hau Giang canal and first part of the Rach Gia - HaTien canal.

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3.11 In the south-western section of the Xa No canal, the run-off fromthe dredge spoil is expected to exceed the acid run-off from the bordering fieldswith a factor 4 (without case). When the potential acid sediment is covered withunderlying non-potentially acid sediment (case 1), the acid run-off from the spoillies in the same order of magnitude as the run-off from the land. When low bundsare constructed to maintain the spoil (case 2) a similar amount of acid run-off canbe expected. When low bunds are constructed and the potentially acid sedimentsare covered, acid run-off from the spoil is expected to be only 20% of the acidrun-off from the fields. In this case, increased acid run-off into canals is notexpected to have great impact on the aquatic environment.

3.12 Following a similar argument, dredging in the Tat Cay Tram canalneeds to be done according to case 2 (low bunds, no covering), resulting in a 20%increase of acid run-off. In view of the expected low additional costs of covering,it is recommended to dredge this stretch according to case 3 (low bunds andcovering), resulting in an increase of only 10% acid run-off.

3.13 In the Tram Canh Den canal dredging should be executed accordingto case 5 (high bunds and covering) still resulting in an increase of acid run-off of45%.

3.14 In the Lap Vo Sa Dec canal high bunds need to be constructed (case4) resulting in an additional run-off from the dredge spoil having the same orderof magnitude as the acid run-off from the small area's with acid sulphate soilsalong this canal. In the cross-section studied, the non-potentially acid sedimentwas found below the projected canal bottom. In this case covering is not possible.It is however well possible that in same parts of the canal more shallow non-potentially acid sediments are found. In this case, it is strongly recommended toapply covering (case 5).

3.15 In the Rach Gia - Ha Tien canal, possibilities for covering arerestricted to the north-western parts of the canal. In the south-eastern part (cross-sections Cl 9, C20, C21 and C22), construction of high bunds is recommended(case 4) where possible with covering (case 5), which still increases the acid run-off from the surrounding lands with 2040%. Despite the fact that the increaseof acid run-off in cross-section C21 is limited to 3% of the acid run-off from theadjacent Eucalyptus fields on raised beds, construction of high bunds isrecommended here together with covering (case 5) in view of the large quantitiesof acid run-off in absolute terms. In the most north-western section of the canal(cross-section C23) construction of low bunds and covering suffices (case 4).

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C. Habitat Improvement

3.16 With respect to the development of vegetation in shallow water,there are good conditions for the development of the Nipa palm (Nipa fructicans).This palm is also very useful to man because their leaves can be used for manypurposes. In favourable conditions the development of mangrove vegetation mayalso be expected. Together with the Nipa palm such vegetation is extremelyimportant for fish, shrimps and crabs. They can spawn there and take shelter init. This is especially important for larvae and juvenile fish and other aquatic biota.Moreover, bank vegetation has an important protective function against erosion.

3.17 The recovery of vegetation on the slope of the dredged banks canbe accelerated by planting and seeding new vegetation. Based on the observedvegetation during the field trip the following species could be used:

- The Nipa palm (Nipa fructicans). Shoots of the Nipa can easily be obtainedand planted. Also it is possible to plant the seeds, however crabs like toeat them;In fresh and more acid circumstances Melaleuca leucodenddra may beplanted. It should be appreciated that these trees are wanted by man formany purposes and therefore people will be tempted to remove them;

- In brackish and acid circumstances a small mangrove shrub Exoecariaagallocha may be planted. This shrub will not be used by man and not begrazed on by cattle.

3.18 An option is the use of rolls or locally produced mattresses of wovencoconut fibres. Coconut fibres are rather resistant to rotting and remain intact formany years, especially below the surface. Under anaerobic circumstances they willremain more than hundred years. Within these rolls or mattresses all kinds ofseeds or seedlings can be planted. These objects immediately provide a good bankprotection. The seeds or seedlings can settle and after some time can take overthe function of the rolls or mattresses as bank protection. Applications of thishave been very positively used as shore protection in Europe, Japan, thePhilippines and the U.S.A. About the costs of application of these rolls ormattresses in Vietnam no information was obtained.

3.19 In areas with more strong current, it is recommended to apply rip-rapof stiff clay lumps or stone. Although stone is not a material that can be foundnaturally in the Delta it can provide suitable habitats for fish, shrimp and crab. Thecan find shelter in it. Also the surface of the stone provides possibilities for plantsand small animals to establish themselves. Other aquatic animals will feed on thisbiota. The larger the individual stones are the better (if possible > 0.4 m). Largerstones are more stable so in and between them holes and overhangs will bepresent. This will be appreciated by many species.

3.20 Recovery of the newly created bank can be obtained by plantingshoots of native plants, (no Eucalyptus species indigenous in other countries!).Species that can be planted are:Tamarindus indicus, Albizzia lebbeck, Exoccaria agallodia, Hibiscus tilleaceus,Cassia siamea, C. fistula, Melaleuca leucodendra, Bamboo sp. Tamarindus indicus.

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3.21 These trees should be planted at distances of + 6 m to give otherspecies change to establish themselves. Costs of planting about 200 US$/ha.

3.22 Much better conditions for the aquatic ecosystems can be obtainedby creating areas of shallow water which are connected to the main waterway.In this shallow water, emergent and submergent vegetation can be planted and/orwill develop naturally. The latter containing more ecological values. It also providesthe opportunity for many other biota to use it or to establish themselves in theshallow water or elsewhere. As a result, the fish and shrimp stocks will increasewhich means better yield for the local fishermen and subsequently more proteinsfor the local population. Another important advantage is the presence of morefiltration capacity provided by the vegetation. Pollutants will be eliminated morequickly and partly absorbed by the vegetation itself. Costs of dredging 2.25US$/m3. The dredged spoil may be needed to cover up a spoil containing pyriticsoil. Costs of planting: 200 US$/ha.

3.23 Good conditions for the development of more ecological andeconomic values (edible fish and other biota) can also be obtained by theconstruction of front bank defence (stone). Behind the construction and the bankof the water body shallow water with a dept of about 1 m and at least 5 m widecan be created. This is also possible if there is no need of a front bank defence.

3.24 If a front bank defence has to be made different materials can beused. Even the use of undisturbed stiff clay is possible. If other materials areneeded rip-rap would be the best. Every 20 m there has to be an opening in theconstruction to connect the shallow water zone to the main water body. Thisprevents a to fast sedimentation and gives organisms the opportunity to migratebetween the shallow water and the canal.

3.25 In the shallow water the development of vegetation is possible. Thevegetation creates the opportunities for the settlement of macro fauna, fishes,crustaceans etc. The ecological and the economical value (production of edible fishetc.) will increase significantly when the above solution is implemented.

3.26 Furthermore, one can consider creating a shallow area in front of thebank to reduce the slope to a value less than 1V:3H; the less steep the better itwill be. There is no minimum. All efforts made in this direction mean animprovement of the environmental and ecological conditions in the waterways.

3.27 In a shallow water system, as proposed above, no fishing, trappingor killing of any animal should be allowed. In order for fish, shrimps and other biotato breed and to develop. From within these "sanctuaries" they can disperse overthe rest of the water body to the benefit of the environment and enlarge the yieldof caught fish and shrimps by the fishing population and the fishermen along thewaterways. The fish and shrimps will be attracted by the favourablecircumstances as a result of the proposed habitat improvement measures. Thegreater the availability shelter for the aquatic fauna the grater the stock of fish,shrimp etc. will be. The extra production of fish etc. will be at least 100kg/ha/year. The maximum is estimated to 500 kg/ha/year.

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3.28 Figure 3.01 presents an impression of the successive habitatimprovement measures. It will be clear, that at many locations there will be aconflict of interest between the resettlement aspects and environmental aspectsof the project, while further the cost for widening the canals in order to create abetter habitat, will be considerable. Therefore it is suggested to make optimal useof locations where extra soil has to be excavated for resettlement sites or forcovering acid deposition sites for the creation of shallow breading grounds.

3.29 Most of the stretches that will be dredged contain more brackish oralmost salt water and low pH-values. These circumstances are unsuitable for thedevelopment of malaria mosquitos. If it is known that malaria prevails in thesurroundings of a possible habitat improvement area, then another location shouldbe chosen for constructing such an area.

D. Environmental Management plan and legal Framework

3.30 Based on the findings from field investigation, literature and expertinputs as discussed in the previous paragraphs, an Environmental Mitigation orEnvironmental Management Plan, (EMP), is prepared in line with the OperationalDirective of the World Bank and presented in Part 2 of this report.

3.31 The EMP summarizes the envisaged negative impacts, describesrecommended mitigative measures and the organisation and timing of theirimplementation. Further a monitoring programme is described to monitor the longand short term impacts and the effectiveness of the mitigative measures. Finallythe cost of the monitoring programme and the mitigative measures recommendedare estimated.

3.32 The EMP presented can only be considered a draft. The final EMPwill have to be prepared following the completion of the detailed design.

3.33 In order to obtain a better insight in respect of the responsibilitiesof, in particular, the authorities that will be responsible for the implementation ofthe project and the laws and regulations that govern resettlement issues andenvironmental issues a group of local experts were given the assignment to makean inventory of the current situation.

3.34 Environment is gradually given more attention by the VietnameseAuthorities. Therefor it is recommended to update the inventory when the projectis ready for implementation.

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HAETAT IMPROVEMENT 2

E4A4LOhV ec K ^WATR WS t eT"- Raft SET -

FiAguTr 3.0PattMENT3

.~~~~~~~~~~~aO

Figure 3.01: Habitat Improvement

1-61

REFERENCES

1. Mekong Delta Master plan (VIE/87/031). 1991. Working paper no. 10:Soils. NEDECO, the Netherlands.

2. Brinkman, R., Nguyen Bao Ve, Tran Kim Tinh and M.E.F. van Mensvoort.1986. Acid sulphate materials in the western Mekong Delta. VH-10research report. Dept. of Soil Science, Agricultural university Wageningen.

3. Mensvoort, M.E.F. and Le Quang Tri. 1988. Morphology and genesis ofactual acid sulphate soils without Jarosite in the Ha Tien plain, MekongDelta, Viet Nam. Proceedings Dakar symposium on Acid Sulphate soils, ILRIPublication 44, Wageningen, the Netherlands.

4. Tran Kim Thach (1 987). Geo-morphological map. In the agro-ecologicalmap of the Mekong Delta.

5. Netherlands Delta development team. 1974. Recommendations concerningagricultural development with improved water control in the mekong Delta.Main report. Bangkok.

6. Ton Tat Chieu, Nguyen Cong Pho, Nguyen Van Nhan. 1988. A report onthe establishment of a soil map of the Mekong Delta. Programme 60-B (inVietnamese).

7. Nguyen Bao Ve et al, Soil Dept. of the University of Can Tho, Vietnam inthe framework of the University cooperation between the WageningenAgricultural University and the University of Can Tho, programme VH-1 0and the 60-B project of the Institute of Science and technology VietnamSurvey: 1985-1988.

8. G. Sterk. 1 991. Leaching of acidity from the topsoil of raised beds on acidsulphate soils. Nuffic project VH-10, Dept. of Hydrology, Soil Physics andHydraulics, Wageningen Agricultural University, the Netherlands.

9. Peter Verburg. 1994. Morphology and Genesis of soil & Evaluation of theside effects of a new canal in an acid sulphate soil area in the Plain ofReeds, Vietnam. Projet Recherche-Developpmente de la Plaine des Joncs,Institute for Agricultural Sciences, Ho Chi Minh city, Fonds voorOntwikkelingssamenwerking, Brussel. Dept. of Soil Science and geology.Wageningen Agricultural University, the Netherlands.

10. Callinan, R.B., G.C. Fraser and M.D. Melville. 1992. Seasonally recurrentfish mortalities and ulcerative disease outbreaks associated with acidsulphate soils in Australian estuaries. In: Selected papers of the Ho Chiminh City symposium on acid sulphate soils, eds. D.L. Dent and M.E.F. vanMensvoort; ILRI publication 53, Wageningen, the Netherlands.

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11. Willett, I.R., M.D. Melville, I. White. 1992. Acid drain waters from potentialacid sulphate soils and their impact on estuarine ecosystems. In: Selectedpapers of the Ho Chi minh City symposium on acid sulphate soils, eds. D.L.Dent and M.E.F. van Mensvoort; ILRI publication 53, Wageningen, theNetherlands.

12. Chiaruddin, lriansyah, O.Klepper and H.D. Rijksen. 1990. Environmentaland socio-economic aspects of fish and fisheries in an area of acid sulphatesoils: Pulau Petak, Indonesia. Papers workshop on acid sulphate soils in thehumid tropics. AARD & LAWOO, Bogor, 1990.

13. Hanhart, K. and Duong Van Ni. 1995. Development of suitable soil andwater management practices on severe acid sulphate soils, series ofexperiments in the Hoa An station, Hau Giang Province, Viet Nam.Wageningen Agricultural University, Wageningen, the Netherlands.

14. Mekong Delta Masterplan (VIE/87/031) Thematic study on environmentalimpacts, February 1993:Volume 1: Main report environmental profileVolume 2: Sensitive ecosystems in the Mekong DeltaVolume 3: Existing ecological conditions and present status ofenvironmental protection and guidelines for environmental protection andmonitoring.Volume 4: Indicative assessment of long-term impacts of salinity intrusionand control and indicative assessment of environmental impacts related tosalt water leaching for the improvement of acid sulphate soils.Volume 5: Indicative assessment of long-term impacts of agriculturalintensification on water quality.

15. Development of suitable soil and water management practices on severeacid sulphate soils, series of experiments in the Hoa An station, Hau GiangProvince, Viet Nam. 1985. Karel Hanhart, Wageningen AgriculturalUniversity Wageningen, the Netherlands and Duong Van Ni, Can ThoUniversity, Viet Nam.

16. NEDECO/MDMP. water Quality in the Mekong Delta, October, 1 991, 40pp.

17. Pham Thi Dung. Water Quality in the Mekong River, Viet Nam, workshopon WQ Project, Vientiane, 17-26 April, 1991.

18. EPC. Chemical and Biological Data on Water Quality of the West VaicoRiver and Plain of reeds. A Report Prepared for NEDECO, September, 1992.

1 9. Tran Minh Chi, Le Quang Han (EPC). Ground Water Quality in the SouthernProvince. Environmental Workshop, Ho Chi Minh City, 1990 (in Viet-namese), 6 pp.

20. WHO Guideline for Drinking Water Quality V.I. Recommendation. Geneva,1984.

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21. MOH. Guidelines for Sanitation and Health Protection- Decree N29, 21October 1971, Medical Publishing House, Ha Noi, 1977, 158 pp (inVietnamese).

22. FAO. Guidelines fcr the Interpretation of Water Quality for Irrigation, 1985.

23. Le Tu Trinh. Water Pollution and Control Strategy for the Vietnamese Partin the Mekong Basin. Formulation Workshop on Mekong Basin wideStrategy for Water Pollution Control, bangkok 25-27 May 1 992,34 pp.

24. SIWRPM. Data on Water Quality in the Mekong Main Streams, 1 990.

25. EPC Data on Water Pollution in the Mekong Delta, 1 989-1992. InL.T.Trinh, P.C.Sy. Environmental Aspects of Can Tho and Soc Trangprovinces, 1992, 120 pp (in Vietnamese).

26. Ministry for Agriculture and Food Industry. Decision N. 23/BVTV-KHKT/QD,20 january 1 992.

27. University of Can Tho, Faculty of Fisheries 1996; Final Report Macro FaunaSurvey.

28. University of Can Tho, Faculty of Fisheries 1996; Final Report FisherySurvey.

29. Vietnam Investment Review, by Thai Ha 19 - 25 February 1969;Government moves to protect biodiversity.

30. A Field Guide to the Birds of South-East Asia 1987; King, WoodcockDickinson; Collins London.

PART 2

ENVIRONMENTAL MANAGEMENT PLAN

I

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1. DESCRIPTION OF CANAL STRETCHES AND MEASURES TO BE TAKEN

1.01 Environmental Management Plan, as presented is only preliminaryin nature as the final plan can only be drawn up once the feasibility study has beencompleted. As far as possible, relevant details of the project are given as well asthe mitigating and managing aspects, the implementation of the monitoring andthe responsibilities concerned.

1.02 This management plan must be updated and, if necessary extendedand adapted after the final design is completed.

1.03 Before the final design is completed, part of the monitoringprogramme must be started in order to obtain as much data as possible onsituations where no dredging has been carried out so far.

1.04 Every year, the outcome of the monitoring results should bepresented in a report produced under the responsibility of the Ministry ofTransport, the Bureau for Inland Waterways. In this report the results must becompared and discussed in relation to the short term and long term impacts of theimprovement of the waterways. If possible, measures will be proposed to minimisenegative impacts which surface as a result of the monitoring programmes.

1.05 The monitoring must be carried out in and along the concernedwaterways and the disposal sites. In order to be able to compare the results foundin the concerned waterways some monitoring will have to be carried out in otherwaterways with more or less the same conditions as found in the waterways tobe improved. These sites will have to be selected after the completion of the finaldesign and after having obtained an up-to-date insight into the (future)developments of the 'other' waterways.

1.06 Training programmes must be set up by Vietnamese Institutes onhow to carry out the monitoring programmes.

The institutes involved are:

- The supervisor(s)/contractors. Brief instructions will suffice for those, whowill conduct the monitoring and checks during dredging.

- The University of Can Tho (CTU), Department of Agriculture (Soil andFisheries). The Faculty of Fisheries and the Soil Science Department willbecome part of the Faculty of Agriculture shortly.

- The Sub-institute of Forest inventory and Planning.- The Peoples Committees of the Provinces.

1.07 The monitoring programmes are given in the next chapters. Theinvolved University, institutes and Provincial Peoples Committees are alreadyfamiliar with carrying out the monitoring as proposed. The monitoring programmes(protocols) however, have to be explained to and discussed with said institutes.It is proposed here, that this should come under the responsibility of the NEDECO-consultants when it concerns activities which should start as soon as possible.The remaining parts of the programme will be taken care of by the consultantsresponsible for drawing up the final design.

11-2

2. IDENTIFICATION OF ADVERSE ENVIRONMENTAL IMPACTS

2.01 Impacts of the anticipated works in the main waterways on thewater quality system and related wet environmental system can be divided inbasically three groups:

- short term impacts mainly due to dredging operations;- medium term impacts due to the oxidation of acid sulphate soils and

destruction of macro fauna on the bottom of the waterways;- long term impacts due to changed hydraulic conditions and changes in the

utilisation of the waterways including the banks.

A. Short term impacts

2.02 The dredging will be carried out by cutter dredgers and grabdredgers. The cutter dredgers that will be used to dredge the inland waterwaysmay have a capacity of 500 to 1000 m3/hr. They must be brought to theirdestination by a tug boat. The pipeline used will have a diameter of approximately0.5 m. It is possible to transport the dredged material over a maximum distanceof 2.5 km from the dredging site. If necessary, a booster station could be used toextend the transport distance. The vertical accuracy of the cutter dredger will be0.2 m or more. Horizontally this comes to approximately 1 m or more.The grab dredgers that will be used will be pontoon mounted grab cranes, whilealso land based excavators may be used.

a) Negative imDacts of dredging

2.03 The negative impacts of dredging can be listed as follows:

a) Disturbance end re-suspension of (polluted) sediments during the dredgingoperations and mixing of non polluted or pyritic layers to be excavated withnon polluted or acid layers.

b) Removal of the top layer of the soil which contains the soft bottom macrofauna.

c) Damage to the natural environment on the canal banks when depositingdredged material, laying or moving the pipeline, or operating a land basedexcavator.

d) Possible leakage of acid or polluted dredged material during transport.e) Spill of bilge water, oil, waste etc.f) Noise disturbancesg) Pollution of surface water due to discharge of excess water from the

disposal areas. Particularly when cutter dredgers are used that make useof hydraulic transport, the return water flow and potential impacts can beconsiderable.

h) Limited use of the disposal area for about half to one year for any purposewhen applying cutter dredgers.

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b) Mitigative measures

2.04 The mitigative measures are:

- In areas where acid layers occur dredging should be done in layers:- The top layer which is normally free of acid, but could contain tree roots

and building remains can best be removed by grab dredger or excavator.The material can be used for creating new dikes, preparation forresettlement sites or dredge deposit containment bunds.

- The underlying potentially acid layer will have to be dredged with due care.The material should be dredged in layers of about 1.50 m to reducespillage.

- The cutter head or grab should not be allowed to move deeper than thelowest boundary of the acid layer, while a second clean-up dredging cutshould be introduced to remove as much acid soil from the under layingnon-acid layer.

- The third layer of clean soil mixed with some spillage from the acid layercan be dredged with over depth and used for covering the deposit ofpotentially acid dredged material.

2.05 In order to reduce the impact of the spreading of acid soil to thesurrounding waterway stretches the movement and resettlement of suspendedmaterial should, or be restricted in order to allow for its removal during a seconddredging cut, or maximum movement should be achieved in order to promotemaximum mixing and thinly spreading which will reduce damage to the macrofauna. Due to the tidal movements in the canals the use of dredging screens is notpossible. It is recommended to carry out the dredging operations in the Xa Nocanal to Ca Mau during the wet season. Then, the transport capacity in thedirection of the sea will be maximum, while the sediment load will be relativelyhigh. In the already more disturbed system of the Rach Gia - Ha Tien canaldredging is also possible during the dry season, since little macro fauna is foundthere.

2.06 Dredging must be done in upstream direction, in order to allow freshwater species to escape from unfavourable conditions. The lateral canals must notto be closed off in order to give better opportunities to the aquatic fauna to avoidthe dredging.

- This negative impact cannot be avoided. The extend of destruction,however, can be limited by applying widening at one side of the waterwayonly, which will also promote the fast resettlement of macro fauna.

- The joining of sections of the pipeline should be carried out by smallmovable cranes. Also, some bunds building must be done in order to lay abase for the pipe.

- The pipe must be laid in places where the cranes can have access andmove around. This will be on the bank of the water body. The best solutionis to lay the pipe directly along the road if there is one. The cranes canmove across the road. If there is no road, the cranes will have to moveover the first cleared area where the excavation of the bank is done.

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Leaking of spoil can be prevented by using undamaged pipe sections andcareful construction.

Spill of oil, bilge water etc. can be prevented by storage and by depositingit at well equipped bunker stations. There are probably no such bunkerstations along the waterways. In the scope of the Can Tho port study it isproposed to built such a station. In that case, the bilge water etc. can bestored there.

Unnecessary noise can be avoided when efficient exhaust pipes are usedfor the diesel engines of the dredger.

The return flow of water from the deposition area will only contain smallportions of sediment. The discharge water must be led through an outletstructure and a ditch back to the canal after it is remained for at least 1 2hours in the deposition site. This will give the sediments the opportunityto separate from the water fraction.From laboratory tests it has appeared, that only after a few days oxidationand release of acid and metal ions from a clay water mixture becomesmeasurable. During these first days most transport water will have flownback to the waterway. During many more month consolidation of thedeposited will continue and pore water will drain from the area. Althoughthe oxidizing circumstances will quickly change to reducing, a proper checkon the quality of the water draining from the deposition area to thewaterways is important.

The options to increase the speed of the consolidation and ripening of thedeposits are limited. In general the ripening will speed-up, when layerthickness is limited and drainage is improved.

c) Institutional Arranoements

2.07 The mitigating measures described above should be described in thetender documents for the dredging works and be incorporated in the contractbetween Employer and Contractor who will receive the dredging assignment.The responsibility for proper implementation therefor lies initially with theEmployer, thus the Ministry of Transport, bureau for Inland Waterways, probablyrepresented by the PMU. Following signing of the contract, the Contractorbecomes the responsible party for the implementation of the measures, while theContract Supervisor will have to ensure that the guide-lines are being followed andfurther instructions are be given.

2.08 During the execution of the works the detection of the position ofthe potential acid layers in particular will require full intention. Although colour andstructures supported by some simple field test provides can provide goodindications, the assistance of the Can Tho University to give initial support andtraining of the supervisors and provide back-up assistance for testing of samplesin the laboratory is most important.

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d) Implementation Schedule

2.09 The elements for the implementation schedule related to the shortterm impacts are:

- Description of mitigative measures in tender and contract documents.Action during preparation of documents;

- Contracting of dredge contractor to implement measures is part of theassignment of the contractor;

- Preparing and agreeing an assignment for the assistance of Can ThoUniversity in relation to the detection of potential acid soils should becompleted prior to the start of the works;

- Also prior to the start of the works the supervisor(s) will have to beassigned and instructed and acceptable arrangements will have to be madefor the storage and treatment of waste from the dredging plant includingoil products.

e) Monitoring and rePorting

2.10 The "monitoring" of the implementation of the prescribed mitigativemeasures in the contract should be done by the Supervisor as part of his dailysupervising activities. He also should be responsible on the reporting of theimplementation of the measures and any deviations as part of his usual reportingobligations.

2.11 His reports should also cover the results of soil and water qualitytests, even when a third party performs the actual tests on request of theSupervisor.

2.12 The acid content at the dredging location and in the return waterditch(es) will have to be measured at regular intervals, (at least every two days),and compared with the acid content in the receiving water body. An increase of20 % of acidity due to the dredging operations is considered critical and will haveto result in adjustments of the operations and warning of parties concerned. Thesemonitoring activities should, preferably, be entrusted to an independent partyassigned by the Employer. For practical reasons also the Supervisor could beinstructed to take care of these measurements, while back-up support from CanTho University and local IWT authorities could be provided.

f) Cost Estimates

2.13 Some required measures can be considered as "normal"requirements for a dredging work and therefor no additional cost will occur. Thisapplies for measures in relation to the negative impacts d,e,f and c to a certainextend.

2.14 Other negative impacts are unavoidable like impact b and h, and cand g to a certain extend. The negative effects will disappear after a few years.Replanting of vegetation along the newly excavated slopes, will not only benefitthe environment but also result in a better protection of the slopes against erosion.The cost will be about 200 US$/ha.

11-6

2.1 5 Important additional cost result from restricted dredging methods asdescribed to avoid mixing of acid and non-acid layers and the covering of potentialacid deposits with "clean" soil. The dredging price is expected to increase withabout 25 % or about 0.50 US$/m3 in areas where dredging in layers due to thepresence of acid layers and need to use the lowest layer for covering the aciddeposit is required. The cost of covering operations will be discussed in the nextchapters.

2.16 Other cost result from the monitoring of water quality and testingof water and soil samples. These cost are estimated at about 25,000 US$. Theyinclude testing support by Can Tho University: 3,000 US$, training: 5,000 US$,expert advices: 11,000 US$, test equipment and materials: 1,000 US$ and costactual monitoring by sampling 5,000 US$.

2.17 For storage and removal of waste and oil products a budget of10,000 US$ will be required if no proper measures are implemented prior to thestart of the works.

B. Medium and long term impacts

a) Identification of negative impacts

2.18 The medium and long term negative impacts are partly the sameimpacts as mentioned under short term impact, as far as these impacts have aneffect after completion of the implementation phase of the project. For an otherpart they result from the changed use of waterways and canal banks.

2.19 The following negative impacts are expected:

- underdeveloped vegetation, macro fauna and fish population as a result ofslow recovery of the destruction of part of flora and fauna during theproject implementation phase.

negative effects on the water quality due to the release of the acid andmetal ions during a number of years from the deposition areas.

the effects of partly destructed habitat and food sources and increasedacidity on commercial fish, shrimp and crab populations.

the effects of acid and metal ions and saline water draining from dredgedeposits on crops.

the effects of increased inland water transport and related development ofshore based facilities on water quality, vegetation, macro fauna and fishpopulations.

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b) Mitigation Measures

2.20 The following mitigative measures can be taken:

The destruction of part of the vegetation and macro fauna during wideningand or deepening of the canals is unavoidable and the effect may benoticeable during a number of years after completion of the works. Asalready indicated in the previous chapter the impact can be reduced by onesided widening of canals, which will promote the resettlement of macrofauna species and by replanting schemes.

The release of acid itself and its impact on water fauna can be reducedconsiderable by using containment bunds and increasing the height of thedeposits, which will reduce the surface from where acid can be washedinto the canals. Covering the deposits with "clean" soil will reduce therelease of acid further. By comparing the "natural" run-off of acid in thearea with the expected run-off of acid from the dredge deposit, a sensibledecision can be taken on the extend of the mitigative measures to betaken. For the following 6 base cases of measures the release of acid asa percentage of the "natural" release is calculated and presented in Table2.01 below, while the preferred options are underlined.

Mitigation options:case 0: without case, no bunds, H = 0.2 m, no coveringcase 1: no bunds, H = 0.2 m, coveringcase 2: low bunds, H = 1.0 m, no coveringcase 3: low bunds, H = 1.0 m, coveringcase 4: high bunds, H = 2.0 m, no coveringcase 5: high bunds, H = 2.0 m, covering

Table 2.01

-case: 0 1 2 3 4 5canal: profile % % % % % %

Cho Gao C1 - - - -

Mang Thit C2 0 0 0 0 0 0Xa No C3 - - - - - -

C4 - - - - -

C5 442 88 88 18 44 9Tat Cay Tram C6 100 50 20 10 10 5Tram Canh Den C7 - - - - - -

C8 907 454 181 91 91 45C9 - - , -

Lap Vo-Sa Dec C12 877 877 175 175 88 88Rach Soi-Hau Giang C13 - - - - -

C14 0 0 0 0 0 0C15 0 0 0 0 0 0C16 0 0 0 0 0 0C17 - - - - -

Rach Gia-Ha Tien Cis - - - - -C19 360 360 72 72 36 36C20 438 438 88 88 44 44C21 52 26 10 5 5 3C22 196 196 39 39 20 20C23 79 40 16 8 8 4

11-8

2.21 From a financial point of view case 4 is much cheaper than option3 or 5, as covering of acid soil deposited by a cutter dredger will only be possibleafter considerable time when the material has settled and ripened sufficiently. Atthat time dry earth moving equipment can still not enter the area but a cutterdredger could deposit a second layer without stirring up the previous layers. This,however, will involve double mobilization and positioning of pipe lines. Thereforeit is recommended to make use of the measure described by case 4 as much aspossible in acid areas and to use case 5 only if an important improvement can beachieved by doing so. In fact only for location C5 in Xa No canal and location C8in Tram Canh Den canal this will be the case. For all other acid areas case 4 canbe applied.

c) The impacts described under 2.20 could well result in a decrease ofcommercial fish, shrimp and crab populations in the canals. The envisagedreduction in catch could be compensated by creating additional breadinggrounds by creating shallow water areas at suitable locations.

d) The adverse effects of acid or salt water draining to the agricultural fieldscan be avoided by using bunds along the deposition sites and excavate aditch around to collect for drainage of any seepage water from the fill.

e) The effect of intensified use of the waterways will to a certain extend becompensated by an increased flushing of the canals as a result of widercross sections, while further the removal of part of the population from thebanks will have a beneficial effect. In fact the impact is expected to be farless important than the increase of pollution of the waterways due to otherfactors like pesticides and nutrients from agricultural fields and untreateddisposal of waste water from villages and townships on the canals.Development of the awareness on environmental issues in general thereforis most important.

c) Institutional arranQements

2.22 The mitigative measures described in the previous paragraph shouldall be described in the tender documents and contract with the contractor who willexecute the works. Thus the Employer will be responsible for the properdescription of the measures in the documents, the Contractor is responsible forthe implementation of the measures, while the Supervisor should make sure thatthe implementation takes place in accordance with the intentions of the contract.

2.23 As far as the planting schemes are concerned also local populationcould be utilized under the guidance and supervision of the Provincial PeoplesCommittees. The involvement of locals may have a positive effect on theawareness of the importance of the habitat created.

2.24 Monitoring of the impact of the project on the environmental aftercompletion of the works may be entrusted to trained members of the ProvincialPeoples Committees with back up assistance from Can Tho University and otherconsultancy experts.

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d) Implementation Schedule

2.25 The elements forthe implementation schedule related to the mediumand long term impacts are:

- Description of the measures in the tender documents prior to the tenderingof the works.

- Incorporating the same in the contract documents prior to signing of thecontracts.

- Implementing the measures as part of the works.- Monitoring the effects during and following the completion of the works

over a period of about 3 years. (the actual duration will depend on theobserved changes taking place).

- If planting schemes are implemented by other parties their activities canstart after the contractor has vacated the area concerned in order to avoidmixing of responsibilities. Preparations and training should precede theactual planting activities.

e) Monitoring and Reporting Procedures

2.26 The proper implementation of the mitigative measures should bemonitored and reported by the Supervisor. After the works have beenimplemented, the deposits of acid material should be maintained properly till theformation of acid has reached "natural" levels while furthermore the impacts ofthe works on the environment will have to be monitored.

2.27 Therefore the following monitoring activities will be required:

- Every 3 months, and especially at the onset of the rainy season, the spoilsshould be checked on possible damages to the bunds and collector drains.The process of setting of the spoil will be observed. All findings must beadministered in a logbook (computer). For every spoil a logbook is needed.The checks will be carried out by trained members of the Provincial PeoplesCommittees. Assuming the spoil will be about 500 x 200 m, 4 spoils perday can be checked by 2 persons.

- In May, the water in the collector drain will be checked on acidity. As soonas exceeds the pH of natural drains with 20 % and becomes 5pH or less,an expert of the university of Can Tho (soil department) must be consulted.He/she will also have to advise if the three monthly checks can be stopped.

- After the dredging is finished, the following parameters of the canals mustbe monitored:

a) Visibilityb) ECc) Acidity (pH)d) Salinitye) Soft bottom macro fauna developmentf) Fish shrimp and crab developmentg) Development of shallow water and bank vegetation.

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2.28 This monitoring of a/f could best be carried out by the University ofCan Tho, Fisheries Department. g could be done by the Sub-Institute of ForestInventory and Planning. The recommended locations for monitoring are: position4, 9, 12, 14, 17, 20, and 21. (see Figure 2.01).

2.29 With respect to the parameters that will have to be monitored listedunder iii) the following applies:

Visibility

2.30 The visibility of water must be measured by a secci disc. This givesinformation on the amount of sediments and algae in the water. It is expected thatthe visibility of the water will increase in the case of lower pH-levels. This effectis the result of less algae and flocculation and sedimentation of small particles inthe water. If this is found together with lower pH-levels it must be caused by anincreased acidity in the water.

Electric Conductivity

2.31 Electric conductivity (EC) gives information about the amount of ionsin the water. In case of increased acidity, the EC will increase. To determinewhether or not changes in EC are the result of changes in salinity, acidity or both,the results of the measured EC-values must to be compared with the data of thepH. In case of doubt, the salinity may be measured too.

pH value

2.32 Monitoring the development of the pH-values will give the bestinformation about acidity in the water body concerned. Particularly, at the start ofthe rainy season (May) an important increase in acidity can be expected, as therun off from the land and deposition sites is expected to influence the acidity inthe canals to a maximum. The measurements should at least cover this period ofthe year.

Salinity

2.33 In order to determine the amount of salt intrusion related to thedredging, the salinity has to be measured in May at the end of the dry season. Thepossible intrusion of salt water may be expected to be at its maximum during thisperiod. If there is some tidal influence in the concerning water body themeasurements have to be carried out during high tide.

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Macro fauna

2.34 Macro fauna develops on and between hard substrate such asplants, wood, stone etc. and on and in the soil. The macro fauna is of greatimportance to fish and other animals that feed on it. The macro fauna itself mainlybelongs to the group of secondary producers. This means that the macro faunamainly feeds on primary producers such as bacteria, algae and water plants.Due to lack of hard substrate, water vegetation etc. the soft bottom macro faunawill be the most important group in terms of biomass in the waterways.Macro fauna living in the soft bottom is, in general, strictly constricted to a certainplace. Therefore, the macro fauna depends on local environmental factors. Theyreflect (indicate) the local conditions of the aquatic environment.

2.35 The influence on mnacro fauna, that lives on and in the bottom is atits maximum during the dredging. After dredging the development of a macrofauna community at the dredged sites has to start from zero.The idea is to monitor the macro fauna in cross sections. As dredging will mainlybe carried out at one side of the waterway, the sampling will include the affectedas well as the not affected bottom in one cross section.In this way, information can be obtained on the influence of the dredging on theexisting macro fauna communities and also on the resettling of macro fauna in thenewly created bottoms.

2.36 In respect of the frequency of sampling it is proposed to carry outthe monitoring at least three times a year. Because of the fact that the macrofauna, in general, does not react very quickly to changes in the environment it isnot important to take samples at a specific time of the year. However, for propercomparison of the measuring results the samples should be taken in the samemonth every year after the programme has started. Also the related parametersshould be measured at the same time of the year.

2.37 At each location one sample will consist of 10 samples of 300 cm2taken with a Petersen grab; at about 2 m depth at both sides of the waterway.The opening mouth of the grab is 15 cm wide and 20 cm long.The sample has to be washed through a messing sieve with a mess width of 05mm. The organisms will have to be collected and preserved in 4 - 6%formaldehyde. The sampled macro fauna must be analyzed and shall provideinformation on:

A. Species composition and abundance per species.B. If possible, the biomass in ash free dry weight per surface unit.C. If possible, the Shannon-Weaver diversity-index should be applied.D. Indicator species for parameters as pH, salinity, pesticides

Fish, shrimps, crabs and shellfish

2.38 Because of their natural values and because they are in principle amain source of proteins to man it is important to monitor the development of fish,shrimps, crab and shellfish populations in the dredged waterways. To monitor theabundance and species composition of these mobile fauna components is not easyand requires a relatively extensive programme of fishing efforts with differenttypes of fishing year.

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2.39 This seems highly impracticable. Therefore it is proposed to set upa system with relies on the co-operation of local fishermen. They will beinterviewed about species and abundance of fish, shrimps, crabs and shell fishfour times a year. The set of questions is given below:

1. What species of fish, shrimp, crab and edible shellfish can be found in thewater body?

2. Which are the local fishing methods used?3. The estimate number of fishermen and used fishing methods per km.4. Has the production increased/decreased over the last three months?;5. If yes, what are the causes?

2.40 A selected number of fishermen will receive a special container withformaldehyde in which they will be asked to collect at least one specimen of eachspecies caught within 500 m upstream and 500 m downstream a specificlocation.

2.41 A complicating factor is the over fishing which is already going onin the canals and adjacent waters. It may therefore be difficult to determinewhether changes in species composition and abundance is caused by dredging,over fishing or both. Yet, it may be expected that evident changes in speciescomposition can be referred back to effects of the project. For the same reasonalso other locations must be surveyed in order to be able to differentiate betweenproject related and non-project related impacts. The locations for back-groundmeasurements will be determined after the completion of the final design.

Shallow water and bank vegetation

2.42 After the final design has been completed, the monitoringprogramme can be prepared for monitoring the developments of the shallow waterand bank vegetation. The monitoring could be carried out by the Sub-institute ofForest Inventor and Planning.

2.43 Should the monitoring show any unexpected and unacceptablenegative impacts, then the possibility of taking mitigating measures will be ratherlimited. This largely depends of future possibilities to influence the flow rate of thewater in a certain stretch of a canal. The main reason for monitoring the proposedparameters is to gain insight in the actual situation and to increase knowledge onthe environmental impacts of similar projects. Reports on the results of the yearlymonitoring campaigns should be prepared by the institution concerned andpresented to the Ministry of Transport, the bureau for Inland Waterways.

11-1 3

Cost estimates

2.44 The cost for monitoring the medium and long term impacts by CanTho University are estimated at 1 5,000 US$/year. Monitoring of deposition areasand development of shallow water and bank vegetation may require an other5,000 US$/year, while some 1 5,000 US$ may be reserved for expert support andguidance.

2.45 The construction of containment bunds and ditches around thedisposal areas should me considered normal practice (although not always usedin the delta) and will not result in extra environmental cost. The same applies for"high" bunds, that are often even cheaper than "low" bunds. Covering of deposits,however, will lead to extra cost of about 0.50 - 1.0 US$ extra per m2 of fill thatwill have to be covered by clean soil. This price increase results from the secondtime of mobilizing the dredger and placing the transport pipeline.

2.46 If covering operations will be implemented for location C5 and C8at Xa No canal and Tram Canh Den canal, the area to be covered will be about 16ha, resulting in extra 1 25,000 US$ of extra cost. The extra cost for dredging inlayers and introducing an extra cleaning up cut, as described in chapter A, for thisarea will result in extra cost of about 200,000 US$, (US$ 0.50 x 400,000 m 3 ).

2.47 For replanting vegetation a price of about US$ 200/ha for a stretchof 10 m width over a total length of 300 km, the cost for replanting would be60,000 US$, which seems very reasonable when compared with the project cost.

2.48 The cost of the creation of shallow breading grounds depends on theneed to collect clay in certain areas for preparation of resettling sites or otherpurposes. Assuming a height of the land of + 0.75 m MSL and a tidal variationof 2.00 m will result in the need to remove a layer of at least 2.00 m in order toavoid the shallow pond to run dry during low water. If the soil can not be usedbeneficially the excavation cost will be about 4.50 US$/m2 or 45,000 US$/hawhich is too expensive for the fish production of 100 to 500 kg/ha. If, however,excavation is needed for other purposes ponds can improve the fish productionvery well, while cost could be limited to the cost for planting vegetation of 200US$/ha.

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3. DESCRIPTION OF CANAL STRETCHES AND MEASURES TO BE TAKEN

3.01 In the previous chapter impacts, mitigative measures, cost etc weredescribed in general terms. In this chapter a description will be presented of theenvironmental features of the different canals to be improved and the meanapproach to be followed for minimizing damage to the environment.

A. The Cho Gao canal

3.02 This stretch is mainly influenced by the tides even during the wetseason. When the EC was measured during the field trip in October it showed avalue of 4230 US$/m. This indicates brackish water even in the wet season.During the dry season the salinity will increase. Because of tidal mud flats on bothsides of the canal a natural vegetation and other biota could establish and maintainthemselves. This stretch also shows the highest number of fish species.

3.03 The soil samples of 1995 did not show pyrite sediments. Therelatively small amount of dredged material can be disposed in places where it canbe useful to man for building or agricultural purposes. However, the dredgingmaterial will be silty. So it will take some time before it is suitable for agriculture.Experiences elsewhere under similar circumstances indicate that within two yearsthe siltation of the top layer is almost reduced to zero. Attention has to be givento the drainage. This water will also be silted for some time.

3.04 Along the Cho Gao canal some smaller more natural habitats on andbehind the banks can be found. These places must be avoided to be used as spoildeposits. Also, the vulnerable natural vegetation along the canal which also playsan important role in bank protection must be respected and maintained.

3.05 Because of the fact that most of the shallow mud flats and the bankremain in tact no severe negative impacts are expected on the aquatic biota. Dueto the tidal influences it is a dynamic system anyhow. So the different species ofthe aquatic flora and fauna-are well adapted to changes in their environment likedisplacement of sediments etc. Also, there is no need to monitor this stretch inrelation to short and long term effects from dredging. Nevertheless, because of thehigh number of species of fish, shrimp and crab found in 1995 it may be usefulto monitor this stretch.

B. The Mang Thit

3.06 According to the found data on the water quality in the Mang Thitriver there is no salinity, not even in the dry season. However, there may be someunknown salt intrusion in the deeper layers of this water body. Only the bottomof the canal will be dredged over some short distance. There is no pyritecontaining soil. The dredged spoil can be deposited at any location, where it canbe used by man for building or agricultural purposes. The banks of the Mang Thitcanal at the dredging sites are somewhat elevated above their surrounding andhave planted trees, houses, sugar cane and sugar factories. It is recommended todeposit the dredged material at some distance from the canal bank. Because of therelatively small quantities involved, there will be no severe impacts on the aquaticenvironment. No significant negative impacts are to be expected on fish and otherbiota or monitoring is proposed in relation to the dredging or long term impacts.

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C. The Xa No canal

3.07 The Xa No canal will be dredged over a distance of 39 km. Dredgingof the bottom and 5 to 20 m of the right bank is envisage. The banks of the XaNo canal show a relatively high density of houses. The raised beds around and inbetween the houses are planted with coconut, mango, banana, other fruit trees,bamboo, sugar cane etc. Also in some places nypa palms can be found. There areno natural habitats left on the banks or at some distance behind the banks. Inmost places there are rice fields at distances of 1 to 2 km behind the canal bank.A double or triple crop of rice is yielded every year.

3.08 The dredged material in the middle and west part of the canal willcontain pyrite, so there will be acid problems related to the dredged spoil. Theacidity in the southern part (location 5) is very high. The top soil in this part is notacid and the back ground acidity is zero. Due to the expected adverse impactscovering of the dredge deposit with non-pyritic material and high bunds arerecommended.

3.09 Along the Xa No canal it is not recommended to promoteresettlement along the dredged bank of the canal. So the best solution would beto create raised resettlement sites at some distance from the canal and connectthese sites to the Xa No canal by side canals and lateral branches. Suchinfrastructure should promote the development of villages at some distance fromthe canal.

3.10 In this way, a better infrastructure and better circumstances toprotect the environment can be achieved. Also there will be good opportunities toimplement habitat improvement measures by creating shallow ponds. They willgive many benefits for the environment and also for the people living along the XaNo canal.

3.11 To separate the pyrite containing fractions from the other soil layersdredging will have to take place in layers. The use of grab dredgers or excavatorsis recommended and may be the cheapest method for widening the channel andpreparing the resettlement sites.

3.12 Along the dredged stretches it is recommended to create shallowwater areas. Together with the vacated banks they can be planted or seeded.

3.13 Following the above proposed or mentioned solutions it isrecommended to carry out monitoring programmes on fish, vegetation and macro-fauna. If resettlement on the newly created bank is allowed monitoring of thevegetation can be omitted.

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D. The Rach Soi - Hau Giang canal

3.14 Up to about 8 km before Rach Gia the Rach Soi - Hau Giang canalcan be considered as a fresh water canal were salinity does not exceed 4 g NaCIper litre during the dry season. The bottom of the canal and the right bank haveto be dredged. The right bank is not so densely populated as the left bank. Atmost places there are many, mostly planted, trees and shrubs. Outside the village,about 30 % of the banks are covered with houses. Apart from some naturaldeveloped trees and shrubs there is almost no natural habitat present on and alongthe banks of he canal. There are only a few poorly developed Nypa palms nearRach Soi.

3.15 In general, the situation is much like the situation along the Xa Nocanal. The same alternatives can therefore be considered for the resettlement ofthe people. The option of creating new villages away from the canal would be thebest solution for the people and the environment, as a better infrastructure andbetter measures to protect the environment can be realized.

3.16 Further there will be good opportunities to implement the habitatimprovement proposals as described in Volume II, Chapter 6. They will give manybenefits for the environment and also for the people living along the Rach Soi -Hau Giang canal. Financially implementation will only be feasible if additional soilis needed for building of bunds or resettlement sites and when no extraresettlement will result from the creation of shallow breading grounds.

3.1 7 According to the soil survey of November 1995 there is no or onlylittle pyrite containing soil along this stretch. This will make it possible todischarge the dredged material on the fields without restrictions to preventnegative impacts due to acidity. Only at and around location 13 attention has tobe given to acidity.

3.18 It is advised to carry out monitoring programmes on fish, vegetationand macro-fauna of the bottom. This will have to be done at location 14. Ifresettlement of the newly created bank is allowed monitoring of the vegetationcan be omitted.

E. The Rach Gia - Ha Tien canal

3.19 This canal contains brackish to salt water even in the wet season.Due to the ongoing cultivation projects in the areas north east of the canal alreadysevere acidification of this canal is taking place. A pH of 3.8 was measured duringthe survey of February 1996! This was after a severe rain shower which may havecaused a temporary extra acidification. Also, the macro-fauna survey of November1995 did not show any organism. Although this may also be caused by the thicklayer of dead leaves on the sampling locations. The number of fish species in thecanal is low compared to the other water bodies that have been surveyed.However, in February fish were still present.

3.20 The number of houses is less compared to most of the other canals.The number of houses on the northern (right) bank is especially low. East of thejunction with the Ba The canal, only 5 % of the bank is occupied by houses. Onthe other bank where the road is situated, 30% of the bank is occupied by houses.

11-17

3.21 The vegetation on the right bank is rather dense. Also some morenatural vegetation like natural developed trees, shrubs en herbs can be found. Onlynear Rach Gia there are some poorly developed nipa palms. The absence of thispalm may be related to the low pH-levels.

3.22 The hinterland of the right bank is very acid. In some small pondsat some distance of the canal pH- values of around 4 were measured. Yet, thereare paddy fields. They yield two crops per year. The crop in the spring seasonyields 3 to 5 tons per hectare, but the crop in August/September not more thanabout 1 ton per hectare due to the acidification.

3.23 The material to be dredged west of Rach Gia contains pyrite. So acidproblems can be expected. The background acidification, however, is also high asa result of the presence of moderately and severe acid sulphate soils all along thecanals and especially high where recently areas are turned into raised beds for thecultivation of Eucalyptus by the Kien-Tai company (joint venture between the KienGiang Province and a Taiwanese company). As a result already a very high acidityis present and large quantities of acid will be flushed to the sea, where the fishand shrimp populations will be reduced.

3.24 As coverage will hardly be possible due to the absence of cleanbottom layers in the deeper part of the excavation at most locations and thelimited increase of the already high acid load of the canals, use of high bundswithout coverage is recommended along the entire canal. The excavation of thenon/less acid top-layer may be dredged by grab dredger or excavator and used forthe construction of bunds and new resettlement sites.

3.25 Along the Rach Gia Ha Tien canal it is not recommended to havesettlements again along the dredged bank of the canal. So the best solution wouldbe to create raised beds at some distance of the canal and connect them with aside canals with lateral branches with the canal.

3.26 It is recommended to carry out monitoring programmes on waterquality, fish, vegetation and macro fauna. If resettlement of the new created bankis allowed monitoring of the vegetation can be omitted.

I

I

I

INLAND WATERWAYS STRETCHES. v- .2s/: 5IScale, 1': 50O.O )

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HO ClIl Ml tII CITY .

,>'14SW 3^' OA r. r0 THE INLAND WATERWAYSSTRETCHES.

f ef e^t zo C.F,} 9 t~o r n IHO Clil MINII KIEN LUONG HO CHI M(Nfl. CA MAU

N0iO.IOQ ioo r _ | No. Names of Canal. Rver Distance Accumulated Distance Names ot Canal. Rivet NoI.UZ | -- Kmn Distance Km Km ___________KD n m_ i

1Ong Lon Creek 486 4 8 4,8 4 8 Ong Lon CreckI2 Cay Kho Creek 3 5 8 3 8 3 3 5 Cay Kho Creek 2

cit/ > l 3 Can Giuoc River 25 7 340 34 0 25.7 Can Gruoc River 3r 4 / ye! 4 Nuoc Man Canal 2.5 36.5 36 5 2.5 Nuoc Man Canal 4

vi j S~~~~~~~~~~~~~~ ~ ~ V'am Co River 10 0 46.5 46 5 i00 Vam ca RiverM^^ '! 4Sr ' l l 6 taCreek 10.0 56.5 565 100 LaCreek e,

~~~~~~~~~~~~~~ ~~~~~~~~~~~~7 Chon Gao Canal 13.0 69 5 69.5 13 0 Cho Gao CanalAc ;.r \/ tQ5- 8 Ky On Canal 6.8 76 3 76 3 6 B Ky On Canal

< cj=i v,. ... no a09 Mekong River 35 5 11 1.8 111 8 35 5' Mekong River 5J

0~~~~~~~~~~~~~~~~~~~ ~~~~~~~~(up to Chro Lach Canal) (up to Cho Lach) MY TI- K j.o 1 Mekong river 33 0 144.8 120 8 9 0 Cho Lach Canal i

9t / f ). \ \.., )k\g n2 11 (up to My Tt uan canal) * 330 144t8 131.8 11.0 Mekong River It)-~~~~ 11~~~I Mekong River 3.0 147.8 161 6 29 8 Mang Thil River 1'?

rr~~~~~-r ~~~~~e.saa K.~~~~~~~~~~ n,.MO ~~~~~~~(up to SaDee confluence) 174 0 12 4 Mang thit River 112 Sa Dec River 27.5 175.3 177 9 319 Tra On Creek 1.t13 Lap Vo Canal 19.0 194.3 '96.6 18.7 Bassac River 1;I14 Lap Vo Creek 55 199.8 212 6 16 0 Can Tho Creek.15 Bassac River 1.5 201 3 252 2 39.6 Xa No Canal

oar nO A n RF M. ,16 Rach So -Hau Giang 546 255.9 2553 3.1 Cai Nhal CreekCanal 267 8 12 5 Car Ta Creek

17 By - Passes Canal 7.8 263 7 272 d 5 0 Cay Tram Creek 20 19 Rach Gra - Hia Tien Canal 61 3 325 0 284 4 11 6 Nga Ba Dinh Creek 219 Kien Luong Cement 33. 328° 317.9 33 5 Trem Canh Den Canal 22

M 19 Factory 3.0 3280 330.4 125 Trem River 23335 3 4 9 Ong DocRiver 2

340 0 4 7 Tac Thu River 25345.6 5 6 Ganh Hao River 2.

_Mv ~~~~~~~~~~i,) *.Notes

rr*,~, Uu,Cr,C. < 1. Km 0 is at Rach Ong bridge in lIo Chi Minh City.2 - Lenghts of Ihe stretches have been measured from Ihe topographic map 115000 scale and hydtograpF,c maps

-Ih scales at 112000 And 111000.Source: map 11500.000 Net work of INLAND WATERWAYS IN THE LOWER MEKONG DELTA' prepared by

xy x \ s. 'UNION OF WATERBORN TRANSPORT COMPANIES It (WATCO 11)Source THE TRANSPORTATION MASTER PLAN' map 115000 scale ot Rach Gia

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I

APPENDIX I

I~~~~~~~~~~~~~~~~~~~~~~~~

Class 1: clean spoilno restrictions concerning use at sea or on land;

Class 2: slightly contaminated spoilno restrictions if a suitable site at sea or on land can be found;

Class 3: slightly to moderately contaminated spoilcan be disposed off on land or if this is not possible in water, when thedisposal area has been studied thoroughly and found suitable; further-more monitoring of the situation during and after disposal is required;

Class 4: contaminated spoilcan be placed on land only and must be covered by an impermeablelayer;

Class 5: highly contaminated spoilideally should not be dredged; if dredging however is imperative, thespoil should be treated as industrial waste.

Lokatie: Vietnam Sampling location no.: 4' d.d. 29-03-1996

The parameters used for standardization of content:

- The organic content is calculated using (100 - burnt weight) * 0.90 = /O %- The measured clav % (< 2 pm.):''3.47%.

Parame_er Me2sured Concentration class % exceeding class limitconcentration normalized to

standard

METALS condition:a a7n ~~mg/kg 0.50 0.45 0

Mercur, mg/kg 0.14 0.12 0

Coper mg/kg 35.00 27.60 0:T ~ mg/kg 25.00 16.51 0Lead mg/kg 140.00 117.71 1 ( 38 %)

mg/kg 85.00 62.25 0Chromium mg/kg 37.00 27.21 0Arsnic mg/kg 16.00 13.09 0

EQX mg/kg

PAK'sSom 10 PAK's mg/kg 0.24 0.30 0

Volatile halogenated hydrocarbonsTrichnooretheen pg/kgHexachloorethaan pg/kg

Ch oorbenzenenDichloorbenzenen pg/kgTrichloorbenzenen pg/kg.etrachloorbenzenen pg/kgPentachioorbenzeen pg/kg <2.00 < 2.47 0F.exachloorbenzeen pg/kg < 2.00 <2.41 0Chloorbenzenen pg/kg <4.00 < 4.94 0

PCB sPCB-28 pg/kg < 10.00 c 12.35 s 2-CB-52 pg/kg <10.00 c 12.35 s 2P-_B-10,_ Ag/kg <4.00 < 4.94 s 2PCB-128 pg/kg < 4.00 c 4.94 s 2PC3-138 .pFg/kg <4.00 c4.94 s 2PCB-153 pg/kg < 4.00 c4.94 s 2PCB-18C Ig/kg <4.00 c 4.94 s 2S3m. PCBIs (6) pg/kg <36.00 c 44.44 s ;Som PCBs (7) pg/kg <40.00 c 49.38 0

PESTICIDES

Aldrin pg/kg <2.00 c2.47 0Dieldrin 4g/kg <2.00 <2.47 ISam Aidrin/Dieldrin gg/kg c4.00 c4.94 0Endrin pg/kg <2.00 <2.47 s 1Drins pg/kg <6.00 c 7.41 0DDT(incl.D'D en DDE)pg/kg < 12.00 c 14.81 s 2o-Endosulfan/sulft pg/kg <2.00 <2.47 0a-HCH pg/kg < 2.00 c2.47 0B-HCHi pg/kg <2.00 <2.47 s 1T -RCH ag/kg < 2.00 c2.47 5 2HCH-verbindingen pg/kg < 6.00 c7.41 0Heptachloor pg/kg <2.00 < 2.47 0Heptachloorepoxide pg/kg <2.00 < 2.47 0lieptachloor & epOx. pg/kg < 4.00 <4.94 0Chloordaan pg/kgHexachloorbUtadieen pg/kgSom pesticiden pg/kg <34.00 <41.98 0

Lokatie: Vietnam Sampling location no.: 20 d.d. 29-03-1996The parameters used for standardization of content:

- The organic content is calculated using (100 - burnt weight) * 0.90 = 12.60 %C.- The measured clay % (< 2 pim.): 55 %.

Parameter MeasUred Concentration class % exceeding class limitconcentration normalized to

standardMETALS condition

Cadmium mg,/kg 0.50 0.37 0Mercury mg/'kg 0.09 0.07 0Coper mg/kg 37.00 23.97 0Nikkel mg/kg 27.00 14.54 0Lead mg/kg 30.00 21.68 0Zink mg/kg 140.00 83.80 0Chromium mg/kg 40.00 25.00 0Arsnic mg/kg 22.00 15.18 0

EOX mg/kg

PAK' sSom 1C PAK's mg/kg 0.65 0.52 0

Volatile halogenated hydrocarbonsTrzchlooretheen 4g/kgHexachlocrethaan ug/kg

ChlocrbenzenenDichloorbenzenen pg/kgTrichloorbenzenen ug/kgTetrachloorbenzenen pg/kgPentachloorbenzeen pg/kg < 4.00 < 3.17 s 1Hexachloorbenzeen pg/kg < 4.00 c 3.17 5 _

Chloorbenzenen pg/kg < 8.00 < 6.35 0

PCB'sPCB-28 pg/kg < 20.00 < 15.87 5 2PCB-52 pg/kg < 20.00 < 15.87 s 2PCB-101 ug/kg < 8.00 < 6.35 s 2PCB-118 pg/kg < 8.00 c 6.35 s 2PCB-138 ,ug/kg < 8.00 < 6.35 s 2PCB-153 pg/kg < 8.00 6 5.35 s 2PCB-180 ug/kg < 8.00 < 6.35 s 2Som PCBs (6) pg/kg < 72.00 < 57.14 1Som PCB's (7) pg/kg < 80.00 < 63.49 0

PESTICIDESAldrin pg/kg < 4.00 < 3.17 1Dieldrin pg/kg c 4.00 < 3.17 I 1Som Aldrin/Dieldrin gg/kg < 8.00 < 6.35 0Endrin ug/kg < 4.00 < 3.17 s IDrins gg/kg < 12.00 < 9.52 0-DDT(incl.DDD en DDE)/pg/kg 7.00 5.56 1 ( 122 %)d-Endosulfan/sulft pg/kg < 4.00 < 3.17 s 1a-HCH pg/kg < 4.00 c 3.17 19-HCH pg/kg < 4.00 < 3.17 5 1T-HCH pg/kg < 4.00 < 3.17 s 2HCH-verbindingen pg/kg < 12.00 < 9.52 0Heptachloor pg/kg < 4.00 < 3.17 s 1Heptachloorepoxide pg/kg < 4.00 < 3.17 s 1Heptachloor & epox. pg/kg < 8.00 < 6.35 0Chloordaan pg/kgHexachloorbutadieen pg/kgSom pesticides pg/kg 7.00 5.56 0